FULLTEXT DEL 3 AV 4
10-K – 2026-02-20 – lnt-20251231.htm
We have also audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (PCAOB), the Company’s internal control over financial reporting as of December 31, 2025, based on criteria established in Internal Control - Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission and our report dated February 20, 2026, expressed an unqualified opinion on the Company’s internal control over financial reporting. Basis for Opinion These financial statements are the responsibility of the Company’s management. Our responsibility is to express an opinion on the Company’s financial statements based on our audits. We are a public accounting firm registered with the PCAOB and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB. We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion. Critical Audit Matter The critical audit matter communicated below is a matter arising from the current-period audit of the financial statements that was communicated or required to be communicated to the audit committee and that (1) relates to accounts or disclosures that are material to the financial statements and (2) involved our especially challenging, subjective, or complex judgments. The communication of critical audit matters does not alter in any way our opinion on the financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing a separate opinion on the critical audit matter or on the accounts or disclosures to which it relates. Regulatory Accounting - Impact of rate regulation on the financial statements - Refer to Notes 1, 2, and 11 to the financial statements Critical Audit Matter Description Alliant Energy Corporation, through its wholly-owned subsidiaries Interstate Power and Light Company and Wisconsin Power and Light Company, is subject to rate regulation by regulatory agencies. Management has determined it meets the requirements under accounting principles generally accepted in the United States of America to prepare its financial statements applying the Regulated Operations Topic 980 of the Financial Accounting Standards Board’s Accounting Standards Codification. The Company’s rates are subject to regulatory rate-setting processes and periodic earnings oversight. The regulation of rates is premised on the full recovery of prudently incurred costs and a reasonable rate of return on invested capital. Regulatory assets generally represent incurred costs that have been deferred and are probable of recovery in future customer rates. Regulatory liabilities generally represent obligations to make refunds to customers or amounts collected in rates for which the costs have not yet been incurred. The Company’s regulatory assets and regulatory liabilities are recognized in accordance with the rulings of the regulatory agencies. A change in these rulings may result in a material impact on results of operations and the amount of certain assets and liabilities in the financial statements. Future regulatory rulings may impact the carrying value and accounting treatment of certain regulatory assets and regulatory liabilities. 49 Table of Contents We identified the impact of rate regulation as a critical audit matter due to the significant judgments made by management to support its assertions about certain impacted account balances and disclosures and the high degree of subjectivity involved in assessing the impact of relevant future regulatory orders on the financial statements. Management judgments include assessing the likelihood of the recovery of incurred costs and refund of obligations to customers in future rates. Given that management’s accounting judgments are based on assumptions about the outcome of future decisions by the regulatory agencies, auditing these judgments required specialized knowledge of accounting for rate regulation and the rate-setting process due to its inherent complexities. How the Critical Audit Matter Was Addressed in the Audit Our audit procedures related to the regulatory filings by management and the uncertainty of future decisions by the regulatory agencies included the following, among others: • We tested the effectiveness of management’s controls over the evaluation of certain regulatory assets and regulatory liabilities, including the monitoring and evaluation of regulatory developments that may affect the likelihood of recovering costs in future rates or of a future reduction in rates. • We inspected and evaluated the Company’s analysis supporting the probability of recovery for certain regulatory assets or refund to customers or future reduction in customer rates for regulatory liabilities not yet addressed in a regulatory order to assess management’s assertions. • We inquired of management regarding current events impacting the Company and inspected minutes of the board of directors and other committees of the Company and evaluated whether matters were identified that may have an impact on certain recorded regulatory assets and liabilities. • We read relevant regulatory orders, interpretations, filings made by the Company or its stakeholders, and other publicly available information issued by the regulatory agencies that pertain to the Company. We evaluated the external information and assessed whether there are matters in such information that would be contradictory to management’s assertion of probability of recovery of certain regulatory assets or refund of regulatory liabilities, or impact other recorded balances. • We obtained representation from management asserting that regulatory assets recorded in the financial statements are probable of recovery and that obligations to make refunds to customers are appropriately recorded as regulatory liabilities. • We evaluated the Company’s disclosures related to the impacts of rate regulation and regulatory developments, including disclosures related to certain regulatory balances recorded. /s/ Deloitte & Touche LLP Milwaukee, Wisconsin February 20, 2026 We have served as the Company’s auditor since 2002. 50 Table of Contents ALLIANT ENERGY CORPORATION CONSOLIDATED STATEMENTS OF INCOME Year Ended December 31, 2025 2024 2023 (in millions, except per share amounts) Revenues: Electric utility $ 3,697 $ 3,372 $ 3,345 Gas utility 525 465 540 Other utility 51 54 52 Non-utility 89 90 90 Total revenues 4,362 3,981 4,027 Operating expenses: Electric production fuel and purchased power 742 628 736 Electric transmission service 625 613 583 Cost of gas sold 263 224 299 Other operation and maintenance: Asset valuation charge for IPL’s Lansing Generating Station — 60 — Other 740 676 675 Depreciation and amortization 846 772 676 Taxes other than income taxes 121 122 115 Total operating expenses 3,337 3,095 3,084 Operating income 1,025 886 943 Other (income) and deductions: Interest expense 512 449 394 Equity income from unconsolidated investments, net ( 60 ) ( 61 ) ( 61 ) Allowance for funds used during construction ( 89 ) ( 75 ) ( 100 ) Other 1 ( 3 ) 3 Total other (income) and deductions 364 310 236 Income before income taxes 661 576 707 Income tax expense (benefit) ( 149 ) ( 114 ) 4 Net income attributable to Alliant Energy common shareowners $ 810 $ 690 $ 703 Weighted average number of common shares outstanding: Basic 257.0 256.5 253.0 Diluted 257.8 256.8 253.3 Earnings per weighted average common share attributable to Alliant Energy common shareowners: Basic $ 3.15 $ 2.69 $ 2.78 Diluted $ 3.14 $ 2.69 $ 2.78 Refer to accompanying Combined Notes to Consolidated Financial Statements. 51 Table of Contents ALLIANT ENERGY CORPORATION CONSOLIDATED BALANCE SHEETS December 31, 2025 2024 (in millions, except per share and share amounts) ASSETS Current assets: Cash and cash equivalents $ 556 $ 81 Accounts receivable, less allowance for expected credit losses 476 427 Production fuel, at weighted average cost 46 54 Gas stored underground, at weighted average cost 49 55 Materials and supplies, at weighted average cost 193 186 Regulatory assets 155 210 Other 222 171 Total current assets 1,697 1,184 Property, plant and equipment, net 20,344 18,701 Investments: ATC Holdings 463 415 Other 231 224 Total investments 694 639 Other assets: Regulatory assets 2,119 2,064 Deferred charges and other 137 126 Total other assets 2,256 2,190 Total assets $ 24,991 $ 22,714 LIABILITIES AND EQUITY Current liabilities: Current maturities of long-term debt $ 1,074 $ 1,171 Commercial paper 88 558 Accounts payable 498 532 Accrued interest 124 112 Regulatory liabilities 88 69 Other 251 273 Total current liabilities 2,123 2,715 Long-term debt, net (excluding current portion) 10,954 8,677 Other liabilities: Deferred tax liabilities 2,310 2,188 Regulatory liabilities 1,113 959 Pension and other benefit obligations 173 224 Other 984 947 Total other liabilities 4,580 4,318 Commitments and contingencies ( Note 1 6 ) Equity: Alliant Energy Corporation common equity: Common stock - $ 0.01 par value - 480,000,000 shares authorized; 257,137,261 and 256,690,222 shares outstanding 3 3 Additional paid-in capital 3,101 3,060 Retained earnings 4,243 3,954 Accumulated other comprehensive income 1 1 Shares in deferred compensation trust - 367,338 and 372,116 shares at a weighted average cost of $ 39.05 and $ 36.56 per share ( 14 ) ( 14 ) Total Alliant Energy Corporation common equity 7,334 7,004 Total liabilities and equity $ 24,991 $ 22,714 Refer to accompanying Combined Notes to Consolidated Financial Statements. 52 Table of Contents ALLIANT ENERGY CORPORATION CONSOLIDATED STATEMENTS OF CASH FLOWS Year Ended December 31, 2025 2024 2023 (in millions) Cash flows from operating activities: Net income $ 810 $ 690 $ 703 Adjustments to reconcile net income to net cash flows from operating activities: Depreciation and amortization 846 772 676 Deferred tax expense (benefit) and tax credits ( 158 ) ( 117 ) 14 Asset valuation charge for IPL’s Lansing Generating Station — 60 — Other 27 ( 22 ) ( 39 ) Other changes in assets and liabilities: Accounts receivable ( 652 ) ( 547 ) ( 414 ) Derivative assets 6 13 149 Accounts payable 14 96 ( 122 ) Regulatory liabilities 140 ( 103 ) ( 149 ) Deferred income taxes (a) 252 259 84 Other ( 116 ) 66 ( 35 ) Net cash flows from operating activities 1,169 1,167 867 Cash flows used for investing activities: Construction and acquisition expenditures: Utility business ( 2,277 ) ( 2,052 ) ( 1,731 ) Other ( 206 ) ( 197 ) ( 123 ) Cash receipts on sold receivables 628 593 453 Proceeds from sales of partial ownership interests in West Riverside — 123 120 Other ( 41 ) ( 14 ) ( 120 ) Net cash flows used for investing activities ( 1,896 ) ( 1,547 ) ( 1,401 ) Cash flows from financing activities: Common stock dividends ( 521 ) ( 492 ) ( 456 ) Proceeds from issuance of common stock, net 23 23 246 Proceeds from issuance of long-term debt 2,470 1,613 1,455 Payments to retire long-term debt ( 300 ) ( 809 ) ( 508 ) Net change in commercial paper ( 470 ) 83 ( 167 ) Other — ( 20 ) 3 Net cash flows from financing activities 1,202 398 573 Net increase in cash, cash equivalents and restricted cash 475 18 39 Cash, cash equivalents and restricted cash at beginning of period 81 63 24 Cash, cash equivalents and restricted cash at end of period $ 556 $ 81 $ 63 Supplemental cash flows information: Cash (paid) received during the period for: Interest ($ 500 ) ($ 434 ) ($ 378 ) Income taxes, net: Federal (a) $ 271 $ 202 $ 82 State - Iowa ( 5 ) ( 5 ) 6 Total income taxes, net $ 266 $ 197 $ 88 Significant non-cash investing and financing activities: Accrued capital expenditures $ 178 $ 224 $ 364 Beneficial interest obtained in exchange for securitized accounts receivable $ 126 $ 163 $ 216 (a) 2025, 2024 and 2023 include $ 285 million, $ 216 million and $ 98 million, respectively, of proceeds from renewable tax credits transferred to other corporate taxpayers Refer to accompanying Combined Notes to Consolidated Financial Statements. 53 Table of Contents ALLIANT ENERGY CORPORATION CONSOLIDATED STATEMENTS OF EQUITY Accumulated Shares in Additional Other Deferred Total Common Paid-In Retained Comprehensive Compensation Common Stock Capital Earnings Income Trust Equity (in millions) 2023: Beginning balance $ 3 $ 2,777 $ 3,509 $ — ($ 13 ) $ 6,276 Net income attributable to Alliant Energy common shareowners 703 703 Common stock dividends ($ 1.81 per share) ( 456 ) ( 456 ) At-the-market offering program, net and Shareowner Direct Plan issuances 246 246 Equity-based compensation plans and other 7 7 Other comprehensive income, net of tax 1 1 Ending balance 3 3,030 3,756 1 ( 13 ) 6,777 2024: Net income attributable to Alliant Energy common shareowners 690 690 Common stock dividends ($ 1.92 per share) ( 492 ) ( 492 ) Shareowner Direct Plan issuances 23 23 Equity-based compensation plans and other 7 ( 1 ) 6 Ending balance 3 3,060 3,954 1 ( 14 ) 7,004 2025: Net income attributable to Alliant Energy common shareowners 810 810 Common stock dividends ($ 2.03 per share) ( 521 ) ( 521 ) Shareowner Direct Plan issuances 23 23 Equity-based compensation plans and other 18 18 Ending balance $ 3 $ 3,101 $ 4,243 $ 1 ($ 14 ) $ 7,334 Refer to accompanying Combined Notes to Consolidated Financial Statements. 54 Table of Contents REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM To the Shareowner and the Board of Directors of Interstate Power and Light Company: Opinion on the Financial Statements We have audited the accompanying consolidated balance sheets of Interstate Power and Light Company and subsidiaries (the “Company”) as of December 31, 2025 and 2024, the related consolidated statements of income, equity, and cash flows, for each of the three years in the period ended December 31, 2025, and the related notes (collectively referred to as the “financial statements”). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2025 and 2024, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2025, in conformity with accounting principles generally accepted in the United States of America. Basis for Opinion These financial statements are the responsibility of the Company’s management. Our responsibility is to express an opinion on the Company’s financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB. We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. The Company is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. As part of our audits, we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Company’s internal control over financial reporting. Accordingly, we express no such opinion. Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion. Critical Audit Matter The critical audit matter communicated below is a matter arising from the current-period audit of the financial statements that was communicated or required to be communicated to the audit committee and that (1) relates to accounts or disclosures that are material to the financial statements and (2) involved our especially challenging, subjective, or complex judgments. The communication of critical audit matters does not alter in any way our opinion on the financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing a separate opinion on the critical audit matter or on the accounts or disclosures to which it relates. Regulatory Accounting - Impact of rate regulation on the financial statements - Refer to Notes 1, 2 and 11 to the financial statements Critical Audit Matter Description Interstate Power and Light Company is subject to rate regulation by regulatory agencies. Management has determined it meets the requirements under accounting principles generally accepted in the United States of America to prepare its financial statements applying the Regulated Operations Topic 980 of the Financial Accounting Standards Board’s Accounting Standards Codification. The Company’s rates are subject to regulatory rate-setting processes and periodic earnings oversight. The regulation of rates is premised on the full recovery of prudently incurred costs and a reasonable rate of return on invested capital. Regulatory assets generally represent incurred costs that have been deferred and are probable of recovery in future customer rates. Regulatory liabilities generally represent obligations to make refunds to customers or amounts collected in rates for which the costs have not yet been incurred. The Company’s regulatory assets and regulatory liabilities are recognized in accordance with the rulings of the regulatory agencies. A change in these rulings may result in a material impact on results of operations and the amount of certain assets and liabilities in the financial statements. Future regulatory rulings may impact the carrying value and accounting treatment of certain regulatory assets and regulatory liabilities. 55 Table of Contents We identified the impact of rate regulation as a critical audit matter due to the significant judgments made by management to support its assertions about certain impacted account balances and disclosures and the high degree of subjectivity involved in assessing the impact of relevant future regulatory orders on the financial statements. Management judgments include assessing the likelihood of the recovery of incurred costs and refund of obligations to customers in future rates. Given that management’s accounting judgments are based on assumptions about the outcome of future decisions by the regulatory agencies, auditing these judgments required specialized knowledge of accounting for rate regulation and the rate-setting process due to its inherent complexities. How the Critical Audit Matter Was Addressed in the Audit Our audit procedures related to the regulatory filings by management and the uncertainty of future decisions by the regulatory agencies included the following, among others: • We tested the effectiveness of management’s controls over the evaluation of certain regulatory assets and regulatory liabilities, including the monitoring and evaluation of regulatory developments that may affect the likelihood of recovering costs in future rates or of a future reduction in rates. • We inspected and evaluated the Company’s analysis supporting the probability of recovery for certain regulatory assets or refund to customers or future reduction in customer rates for regulatory liabilities not yet addressed in a regulatory order to assess management’s assertions. • We inquired of management regarding current events impacting the Company and inspected minutes of the board of directors and other committees of the Company and evaluated whether matters were identified that may have an impact on certain recorded regulatory assets and liabilities. • We read relevant regulatory orders, interpretations, filings made by the Company or its stakeholders, and other publicly available information issued by the regulatory agencies that pertain to the Company. We evaluated the external information and assessed whether there are matters in such information that would be contradictory to management’s assertion of probability of recovery of certain regulatory assets or refund of regulatory liabilities, or impact other recorded balances. • We obtained representation from management asserting that regulatory assets recorded in the financial statements are probable of recovery and that obligations to make refunds to customers are appropriately recorded as regulatory liabilities. • We evaluated the Company’s disclosures related to the impacts of rate regulation and regulatory developments, including disclosures related to certain regulatory balances recorded. /s/ Deloitte & Touche LLP Milwaukee, Wisconsin February 20, 2026 We have served as the Company’s auditor since 2002. 56 Table of Contents INTERSTATE POWER AND LIGHT COMPANY CONSOLIDATED STATEMENTS OF INCOME Year Ended December 31, 2025 2024 2023 (in millions) Revenues: Electric utility $ 1,896 $ 1,747 $ 1,761 Gas utility 265 250 300 Steam and other 47 49 49 Total revenues 2,208 2,046 2,110 Operating expenses: Electric production fuel and purchased power 283 269 282 Electric transmission service 422 417 420 Cost of gas sold 130 123 166 Other operation and maintenance: Asset valuation charge for IPL’s Lansing Generating Station — 60 — Other 373 358 353 Depreciation and amortization 463 404 388 Taxes other than income taxes 59 60 57 Total operating expenses 1,730 1,691 1,666 Operating income 478 355 444 Other (income) and deductions: Interest expense 211 177 155 Allowance for funds used during construction ( 56 ) ( 43 ) ( 21 ) Other ( 7 ) ( 12 ) 2 Total other (income) and deductions 148 122 136 Income before income taxes 330 233 308 Income tax benefit ( 127 ) ( 129 ) ( 58 ) Net income $ 457 $ 362 $ 366 Earnings per share data is not disclosed given Alliant Energy Corporation is the sole shareowner of all shares of IPL’s common stock outstanding during the periods presented. Refer to accompanying Combined Notes to Consolidated Financial Statements. 57 Table of Contents INTERSTATE POWER AND LIGHT COMPANY CONSOLIDATED BALANCE SHEETS December 31, 2025 2024 (in millions, except per share and share amounts) ASSETS Current assets: Cash and cash equivalents $ 7 $ 29 Accounts receivable, less allowance for expected credit losses 185 192 Production fuel, at weighted average cost 18 30 Gas stored underground, at weighted average cost 24 25 Materials and supplies, at weighted average cost 111 113 Regulatory assets 59 77 Other 58 43 Total current assets 462 509 Property, plant and equipment, net 10,436 9,336 Other assets: Regulatory assets 1,557 1,509 Deferred charges and other 40 53 Total other assets 1,597 1,562 Total assets $ 12,495 $ 11,407 LIABILITIES AND EQUITY Current liabilities: Current maturities of long-term debt $ — $ 300 Commercial paper 88 50 Accounts payable 232 263 Accounts payable to associated companies 45 47 Accrued taxes 53 77 Accrued interest 47 48 Regulatory liabilities 41 54 Other 80 89 Total current liabilities 586 928 Long-term debt, net (excluding current portion) 4,680 3,790 Other liabilities: Deferred tax liabilities 1,278 1,179 Regulatory liabilities 545 492 Pension and other benefit obligations 30 46 Other 532 511 Total other liabilities 2,385 2,228 Commitments and contingencies ( Note 1 6 ) Equity: Interstate Power and Light Company common equity: Common stock - $ 2.50 par value - 24,000,000 shares authorized; 13,370,788 shares outstanding 33 33 Additional paid-in capital 3,497 3,212 Retained earnings 1,314 1,216 Total Interstate Power and Light Company common equity 4,844 4,461 Total liabilities and equity $ 12,495 $ 11,407 Refer to accompanying Combined Notes to Consolidated Financial Statements. 58 Table of Contents INTERSTATE POWER AND LIGHT COMPANY CONSOLIDATED STATEMENTS OF CASH FLOWS Year Ended December 31, 2025 2024 2023 (in millions) Cash flows from operating activities: Net income $ 457 $ 362 $ 366 Adjustments to reconcile net income to net cash flows from operating activities: Depreciation and amortization 463 404 388 Deferred tax expense (benefit) and tax credits ( 96 ) ( 91 ) 8 Asset valuation charge for IPL’s Lansing Generating Station — 60 — Other ( 25 ) ( 12 ) ( 10 ) Other changes in assets and liabilities: Accounts receivable ( 599 ) ( 544 ) ( 437 ) Regulatory assets ( 72 ) ( 2 ) 58 Derivative assets 4 6 84 Regulatory liabilities 20 ( 61 ) ( 92 ) Deferred income taxes (a) 194 178 36 Other ( 60 ) 57 ( 140 ) Net cash flows from operating activities 286 357 261 Cash flows used for investing activities: Construction and acquisition expenditures ( 1,473 ) ( 1,224 ) ( 712 ) Cash receipts on sold receivables 628 593 453 Other ( 14 ) ( 53 ) ( 67 ) Net cash flows used for investing activities ( 859 ) ( 684 ) ( 326 ) Cash flows from financing activities: Common stock dividends ( 359 ) ( 200 ) ( 280 ) Capital contributions from parent 285 325 80 Proceeds from issuance of long-term debt 888 643 296 Payments to retire long-term debt ( 300 ) ( 500 ) — Net change in commercial paper 38 50 — Other ( 1 ) ( 15 ) 7 Net cash flows from financing activities 551 303 103 Net increase (decrease) in cash, cash equivalents and restricted cash ( 22 ) ( 24 ) 38 Cash, cash equivalents and restricted cash at beginning of period 29 53 15 Cash, cash equivalents and restricted cash at end of period $ 7 $ 29 $ 53 Supplemental cash flows information: Cash (paid) received during the period for: Interest ($ 212 ) ($ 169 ) ($ 150 ) Income taxes, net: Federal (a) $ 142 $ 164 $ 98 State - Iowa ( 3 ) 11 19 Total income taxes, net $ 139 $ 175 $ 117 Significant non-cash investing and financing activities: Accrued capital expenditures $ 98 $ 128 $ 140 Beneficial interest obtained in exchange for securitized accounts receivable $ 126 $ 163 $ 216 (a) 2025, 2024 and 2023 include $ 140 million, $ 117 million and $ 76 million, respectively, of proceeds from renewable tax credits transferred to other corporate taxpayers Refer to accompanying Combined Notes to Consolidated Financial Statements. 59 Table of Contents INTERSTATE POWER AND LIGHT COMPANY CONSOLIDATED STATEMENTS OF EQUITY Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity (in millions) 2023: Beginning balance $ 33 $ 2,807 $ 968 $ 3,808 Net income 366 366 Common stock dividends ( 280 ) ( 280 ) Capital contributions from parent 80 80 Ending balance 33 2,887 1,054 3,974 2024: Net income 362 362 Common stock dividends ( 200 ) ( 200 ) Capital contributions from parent 325 325 Ending balance 33 3,212 1,216 4,461 2025: Net income 457 457 Common stock dividends ( 359 ) ( 359 ) Capital contributions from parent 285 285 Ending balance $ 33 $ 3,497 $ 1,314 $ 4,844 Refer to accompanying Combined Notes to Consolidated Financial Statements. 60 Table of Contents REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM To the Shareowner and the Board of Directors of Wisconsin Power and Light Company: Opinion on the Financial Statements We have audited the accompanying consolidated balance sheets of Wisconsin Power and Light Company and subsidiaries (the “Company”) as of December 31, 2025 and 2024, the related consolidated statements of income, equity, and cash flows, for each of the three years in the period ended December 31, 2025, and the related notes (collectively referred to as the “financial statements”). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2025 and 2024, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2025, in conformity with accounting principles generally accepted in the United States of America. Basis for Opinion These financial statements are the responsibility of the Company’s management. Our responsibility is to express an opinion on the Company’s financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB. We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. The Company is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. As part of our audits, we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Company’s internal control over financial reporting. Accordingly, we express no such opinion. Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion. Critical Audit Matter The critical audit matter communicated below is a matter arising from the current-period audit of the financial statements that was communicated or required to be communicated to the audit committee and that (1) relates to accounts or disclosures that are material to the financial statements and (2) involved our especially challenging, subjective, or complex judgments. The communication of critical audit matters does not alter in any way our opinion on the financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing a separate opinion on the critical audit matter or on the accounts or disclosures to which it relates. Regulatory Accounting - Impact of rate regulation on the financial statements - Refer to Notes 1, 2, and 11 to the financial statements Critical Audit Matter Description Wisconsin Power and Light Company is subject to rate regulation by regulatory agencies. Management has determined it meets the requirements under accounting principles generally accepted in the United States of America to prepare its financial statements applying the Regulated Operations Topic 980 of the Financial Accounting Standards Board’s Accounting Standards Codification. The Company’s rates are subject to regulatory rate-setting processes and periodic earnings oversight. The regulation of rates is premised on the full recovery of prudently incurred costs and a reasonable rate of return on invested capital. Regulatory assets generally represent incurred costs that have been deferred and are probable of recovery in future customer rates. Regulatory liabilities generally represent obligations to make refunds to customers or amounts collected in rates for which the costs have not yet been incurred. The Company’s regulatory assets and regulatory liabilities are recognized in accordance with the rulings of the regulatory agencies. A change in these rulings may result in a material impact on results of operations and the amount of certain assets and liabilities in the financial statements. Future regulatory rulings may impact the carrying value and accounting treatment of certain regulatory assets and regulatory liabilities. 61 Table of Contents We identified the impact of rate regulation as a critical audit matter due to the significant judgments made by management to support its assertions about certain impacted account balances and disclosures and the high degree of subjectivity involved in assessing the impact of relevant future regulatory orders on the financial statements. Management judgments include assessing the likelihood of the recovery of incurred costs and refund of obligations to customers in future rates. Given that management’s accounting judgments are based on assumptions about the outcome of future decisions by the regulatory agencies, auditing these judgments required specialized knowledge of accounting for rate regulation and the rate-setting process due to its inherent complexities. How the Critical Audit Matter Was Addressed in the Audit Our audit procedures related to the regulatory filings by management and the uncertainty of future decisions by the regulatory agencies included the following, among others: • We tested the effectiveness of management’s controls over the evaluation of certain regulatory assets and regulatory liabilities, including the monitoring and evaluation of regulatory developments that may affect the likelihood of recovering costs in future rates or of a future reduction in rates. • We inspected and evaluated the Company’s analysis supporting the probability of recovery for certain regulatory assets or refund to customers or future reduction in customer rates for regulatory liabilities not yet addressed in a regulatory order to assess management’s assertions. • We inquired of management regarding current events impacting the Company and inspected minutes of the board of directors and other committees of the Company and evaluated whether matters were identified that may have an impact on certain recorded regulatory assets and liabilities. • We read relevant regulatory orders, interpretations, filings made by the Company or its stakeholders, and other publicly available information issued by the regulatory agencies that pertain to the Company. We evaluated the external information and assessed whether there are matters in such information that would be contradictory to management’s assertion of probability of recovery of certain regulatory assets or refund of regulatory liabilities, or impact other recorded balances. • We obtained representation from management asserting that regulatory assets recorded in the financial statements are probable of recovery and that obligations to make refunds to customers are appropriately recorded as regulatory liabilities. • We evaluated the Company’s disclosures related to the impacts of rate regulation and regulatory developments, including disclosures related to certain regulatory balances recorded. /s/ Deloitte & Touche LLP Milwaukee, Wisconsin February 20, 2026 We have served as the Company’s auditor since 2002. 62 Table of Contents WISCONSIN POWER AND LIGHT COMPANY CONSOLIDATED STATEMENTS OF INCOME Year Ended December 31, 2025 2024 2023 (in millions) Revenues: Electric utility $ 1,801 $ 1,625 $ 1,584 Gas utility 260 215 240 Other 4 5 3 Total revenues 2,065 1,845 1,827 Operating expenses: Electric production fuel and purchased power 459 359 455 Electric transmission service 203 196 163 Cost of gas sold 133 101 134 Other operation and maintenance 306 279 271 Depreciation and amortization 370 357 280 Taxes other than income taxes 55 56 52 Total operating expenses 1,526 1,348 1,355 Operating income 539 497 472 Other (income) and deductions: Interest expense 173 165 149 Allowance for funds used during construction ( 33 ) ( 32 ) ( 79 ) Other 12 8 ( 3 ) Total other (income) and deductions 152 141 67 Income before income taxes 387 356 405 Income tax expense (benefit) ( 14 ) 11 60 Net income $ 401 $ 345 $ 345 Earnings per share data is not disclosed given Alliant Energy Corporation is the sole shareowner of all shares of WPL’s common stock outstanding during the periods presented. Refer to accompanying Combined Notes to Consolidated Financial Statements. 63 Table of Contents WISCONSIN POWER AND LIGHT COMPANY CONSOLIDATED BALANCE SHEETS December 31, 2025 2024 (in millions, except per share and share amounts) ASSETS Current assets: Cash and cash equivalents $ 37 $ 51 Accounts receivable, less allowance for expected credit losses 273 220 Production fuel, at weighted average cost 28 24 Gas stored underground, at weighted average cost 25 30 Materials and supplies, at weighted average cost 81 69 Regulatory assets 96 133 Prepaid gross receipts tax 52 51 Other 59 57 Total current assets 651 635 Property, plant and equipment, net 9,363 8,861 Other assets: Regulatory assets 562 555 Deferred charges and other 79 55 Total other assets 641 610 Total assets $ 10,655 $ 10,106 LIABILITIES AND EQUITY Current liabilities: Commercial paper $ — $ 183 Accounts payable 197 209 Accrued interest 46 44 Regulatory liabilities 47 15 Other 105 94 Total current liabilities 395 545 Long-term debt, net 3,669 3,370 Other liabilities: Deferred tax liabilities 861 865 Regulatory liabilities 568 467 Pension and other benefit obligations 75 102 Other 712 656 Total other liabilities 2,216 2,090 Commitments and contingencies ( Note 1 6 ) Equity: Wisconsin Power and Light Company common equity: Common stock - $ 5 par value - 18,000,000 shares authorized; 13,236,601 shares outstanding 66 66 Additional paid-in capital 2,613 2,533 Retained earnings 1,696 1,502 Total Wisconsin Power and Light Company common equity 4,375 4,101 Total liabilities and equity $ 10,655 $ 10,106 Refer to accompanying Combined Notes to Consolidated Financial Statements. 64 Table of Contents WISCONSIN POWER AND LIGHT COMPANY CONSOLIDATED STATEMENTS OF CASH FLOWS Year Ended December 31, 2025 2024 2023 (in millions) Cash flows from operating activities: Net income $ 401 $ 345 $ 345 Adjustments to reconcile net income to net cash flows from operating activities: Depreciation and amortization 370 357 280 Other ( 63 ) ( 51 ) ( 47 ) Other changes in assets and liabilities: Accounts receivable ( 56 ) ( 5 ) 23 Regulatory assets 43 72 ( 34 ) Regulatory liabilities 120 ( 41 ) ( 57 ) Deferred income taxes (a) 40 84 50 Other ( 19 ) — 18 Net cash flows from operating activities 836 761 578 Cash flows used for investing activities: Construction and acquisition expenditures ( 804 ) ( 828 ) ( 1,019 ) Proceeds from sales of partial ownership interests in West Riverside — 123 120 Other ( 23 ) ( 19 ) ( 47 ) Net cash flows used for investing activities ( 827 ) ( 724 ) ( 946 ) Cash flows from (used for) financing activities: Common stock dividends ( 207 ) ( 196 ) ( 184 ) Capital contributions from parent 80 55 245 Proceeds from issuance of long-term debt 296 297 297 Net change in commercial paper ( 183 ) ( 135 ) 28 Other ( 9 ) ( 14 ) ( 16 ) Net cash flows from (used for) financing activities ( 23 ) 7 370 Net increase (decrease) in cash, cash equivalents and restricted cash ( 14 ) 44 2 Cash, cash equivalents and restricted cash at beginning of period 51 7 5 Cash, cash equivalents and restricted cash at end of period $ 37 $ 51 $ 7 Supplemental cash flows information: Cash (paid) received during the period for: Interest ($ 176 ) ($ 163 ) ($ 146 ) Income taxes, net: Federal (a) $ 124 $ 41 ($ 25 ) State - Wisconsin ( 15 ) ( 27 ) ( 25 ) Total income taxes, net $ 109 $ 14 ($ 50 ) Significant non-cash investing and financing activities: Accrued capital expenditures $ 71 $ 87 $ 217 (a) 2025, 2024 and 2023 include $ 145 million, $ 99 million and $ 22 million, respectively, of proceeds from renewable tax credits transferred to other corporate taxpayers Refer to accompanying Combined Notes to Consolidated Financial Statements. 65 Table of Contents WISCONSIN POWER AND LIGHT COMPANY CONSOLIDATED STATEMENTS OF EQUITY Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity (in millions) 2023: Beginning balance $ 66 $ 2,233 $ 1,192 $ 3,491 Net income 345 345 Common stock dividends ( 184 ) ( 184 ) Capital contributions from parent 245 245 Ending balance 66 2,478 1,353 3,897 2024: Net income 345 345 Common stock dividends ( 196 ) ( 196 ) Capital contributions from parent 55 55 Ending balance 66 2,533 1,502 4,101 2025: Net income 401 401 Common stock dividends ( 207 ) ( 207 ) Capital contributions from parent 80 80 Ending balance $ 66 $ 2,613 $ 1,696 $ 4,375 Refer to accompanying Combined Notes to Consolidated Financial Statements. 66 Table of Contents ALLIANT ENERGY CORPORATION INTERSTATE POWER AND LIGHT COMPANY WISCONSIN POWER AND LIGHT COMPANY COMBINED NOTES TO CONSOLIDATED FINANCIAL STATEMENTS NOTE 1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES NOTE 1 (a) General - Description of Business - Alliant Energy’s financial statements include the accounts of Alliant Energy and its consolidated subsidiaries. Alliant Energy is a Midwest U.S. energy holding company, whose primary wholly-owned subsidiaries are IPL, WPL, AEF and Corporate Services. IPL’s financial statements include the accounts of IPL and its consolidated subsidiaries, including IPL SPE LLC, which is used for IPL’s sales of accounts receivable program. IPL is a direct subsidiary of Alliant Energy and is a public utility engaged principally in the generation and distribution of electricity and the distribution and transportation of natural gas to retail customers in select markets in Iowa. IPL also sells electricity to wholesale customers in Illinois and Iowa. In July 2025, IPL’s wholesale power agreement with Southern Minnesota Energy Cooperative expired. IPL provided steam from its Prairie Creek Generating Station to high-pressure steam customers in Cedar Rapids, Iowa through 2025. WPL’s financial statements include the accounts of WPL and its consolidated subsidiaries. WPL is a direct subsidiary of Alliant Energy and is a public utility engaged principally in the generation and distribution of electricity and the distribution and transportation of natural gas to retail customers in select markets in Wisconsin. WPL also sells electricity to wholesale customers in Wisconsin. AEF is comprised of Travero, ATI, corporate venture investments, a non-utility wind farm, the Sheboygan Falls Energy Facility and other non-utility holdings. Travero includes a short-line rail freight service in Iowa; a Mississippi River barge, rail and truck freight terminal in Illinois; freight brokerage services; and a rail-served warehouse in Iowa. ATI, a wholly-owned subsidiary of AEF, holds all of Alliant Energy’s interest in ATC Holdings. Corporate venture investments includes various minority ownership interests in regional and national venture funds, including a global coalition of energy companies working together to help identify and research innovative technologies and business models within the emerging energy economy. The non-utility wind farm includes a 50 % cash equity ownership interest in a 225 MW wind farm located in Oklahoma. The Sheboygan Falls Energy Facility is a 347 MW, simple-cycle, natural gas-fired EGU near Sheboygan Falls, Wisconsin, which is currently leased to WPL through 2044. Corporate Services is the subsidiary formed to provide administrative services to Alliant Energy and its subsidiaries. Basis of Presentation - The financial statements reflect investments in controlled subsidiaries on a consolidated basis and Alliant Energy’s, IPL’s and WPL’s proportionate shares of jointly-owned utility EGUs. Unconsolidated investments that Alliant Energy and WPL do not control are accounted for under the equity method of accounting. Under the equity method of accounting, Alliant Energy and WPL initially record the investment at cost, and adjust the carrying amount of the investment to recognize their respective share of the earnings or losses of the investee. Dividends received from an investee reduce the carrying amount of the equity investment. Investments that do not meet the criteria for consolidation or the equity method of accounting are accounted for under the cost method. All intercompany balances and transactions, other than certain transactions affecting the rate-making process at IPL and WPL, have been eliminated from the financial statements. Such transactions not eliminated include costs that are recoverable from customers through rate-making processes. The financial statements are prepared in conformity with GAAP, which give recognition to the rate-making practices of FERC and state commissions having regulatory jurisdiction. Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes. Use of Estimates - The preparation of the financial statements requires management to make estimates and assumptions that affect: (a) the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements; and (b) the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. NOTE 1 (b) Regulatory Assets and Regulatory Liabilities - Alliant Energy, IPL and WPL are subject to regulation by FERC and state regulatory commissions in their service territories. As a result, Alliant Energy, IPL and WPL are subject to GAAP provisions for regulated operations, which provide that rate-regulated public utilities record certain costs and credits allowed in the rate-making process in different periods than for non-utility entities. Regulatory assets generally represent incurred costs that have been deferred as such costs are probable of recovery in future customer rates. Regulatory liabilities generally represent obligations to make refunds to customers or amounts collected in rates for which the related costs have not yet been incurred. Amounts recorded as regulatory assets or regulatory liabilities are generally recognized in the income statements at the time they are reflected in rates. 67 Table of Contents NOTE 1 (c) Income Taxes - The liability method of accounting is followed for deferred taxes, which requires the establishment of deferred tax assets and liabilities, as appropriate, for temporary differences between the tax basis of assets and liabilities and the amounts reported in the financial statements. Deferred taxes are recorded using currently enacted tax rates and estimates of state apportionment. Changes in deferred tax assets and liabilities associated with certain property-related differences at IPL are accounted for differently than other subsidiaries of Alliant Energy due to rate-making practices in Iowa. Rate-making practices in Iowa do not allow the impact of certain deferred tax expenses (benefits) to be included in the determination of retail rates. Based on these rate-making practices, deferred tax expense (benefit) related to these property-related differences at IPL is not recorded in the income statement but instead recorded to regulatory assets or regulatory liabilities until these temporary differences reverse. In Wisconsin, the PSCW allows rate recovery of deferred tax expense on all temporary differences. The flow-through method of accounting is used for investment tax credits. Certain federal investment tax credits related to utility property, plant and equipment are subject to statutory tax normalization rules limiting how they may be treated in rate-making. As appropriate to reflect the rate-making practices, investment tax credits are deferred and amortized over the book depreciable lives of the related property or other period prescribed by rate regulation. Alliant Energy files a consolidated federal income tax return and a combined return in Wisconsin, which include Alliant Energy and its subsidiaries. Alliant Energy subsidiaries with a presence in Iowa file as part of a consolidated return in Iowa. Alliant Energy allocates consolidated income tax expense to its subsidiaries that are members of the group that file a consolidated or combined income tax return. IPL and WPL use the separate return approach for calculating their income tax provisions and related deferred tax assets and liabilities. IPL and WPL are assumed to file separate tax returns with the federal and state taxing authorities, except that net operating losses (and other current or deferred tax attributes) are characterized as realized (or realizable) by IPL and WPL when those tax attributes are realized (or realizable) by the consolidated tax return group of Alliant Energy (even if IPL and WPL would not otherwise have realized the attributes on a stand-alone basis). IPL and WPL have entered into agreements to transfer renewable tax credits from certain wind, solar and energy storage facilities to other corporate taxpayers in exchange for cash. Alliant Energy, IPL and WPL have elected to record transfers of renewable tax credits as part of income taxes, and cash received from the transfer of renewable tax credits is recorded in cash flows from operating activities. Renewable tax credits subject to future transfer are recorded at expected realizable value. Renewable tax credits are derecognized when control of the tax credits is transferred to other corporate taxpayers. Beginning October 1, 2024, IPL’s renewable energy rider was discontinued, and production tax credits, excluding production tax credits from the refurbishment of existing wind farms, are credited to IPL’s retail electric customers through its fuel-related cost recovery mechanism. Investment tax credits resulting from IPL’s renewable generation and energy storage projects that are not yet included in base rates may be utilized to offset any revenue deficiency on an annual basis up to IPL’s return on common equity threshold; any remaining investment tax credits, net of the cost of transferability, that are not used to offset any revenue deficiency, will be deferred by IPL and carried forward to offset any potential revenue deficiency in future years. At WPL, pursuant to escrow treatment approved by the PSCW, the difference between actual renewable tax credits and the amount of renewable tax credits collected from customers as electric revenues is recognized in “Income taxes” in Alliant Energy’s and WPL’s income statements. An offsetting amount is recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and WPL’s balance sheets until reflected in future billings to customers. Refer to Note 1 6 (d) for further discussion of the indemnification requirements. NOTE 1 (d) Cash, Cash Equivalents and Restricted Cash - Cash and cash equivalents include short-term liquid investments that have original maturities of less than 90 days. At December 31, 2025, Alliant Energy’s and WPL’s cash and cash equivalents included $ 411 million and $ 25 million, respectively, of money market fund investments, with weighted average interest rates of 4 %. At December 31, 2025 and 2024, Alliant Energy’s restricted cash was not material. NOTE 1 (e) Property, Plant and Equipment - Utility Plant - General - Utility plant is recorded at the original cost of acquisition or construction, which includes material, labor, contractor services, AFUDC and allocable overheads, such as supervision, engineering, certain administrative costs directly related to construction, benefits, certain taxes and transportation. Repairs, replacements and renewals of items of property determined to be less than a unit of property or that do not increase the property’s life or functionality are charged to maintenance expense. Property, plant and equipment that is probable of being retired early is classified as plant anticipated to be retired early. Generally, ordinary retirements of utility plant and salvage value are netted and charged to accumulated depreciation upon removal from utility plant accounts and no gain or loss is recognized consistent with rate-making principles. However, if regulators have approved recovery of the remaining net book value of property, plant and equipment that is retired early, or such approval by regulators is probable, the remaining net book value is reclassified from property, plant and equipment to regulatory assets upon retirement. 68 Table of Contents Depreciation - IPL and WPL use a combination of remaining life and straight-line depreciation methods as approved by their respective regulatory commissions. The composite or group method of depreciation is used, in which a single depreciation rate is applied to the gross investment in a particular class of property. This method pools similar assets and then depreciates each group as a whole. Periodic depreciation studies are performed to determine the appropriate group lives, net salvage, estimated cost of removal and group depreciation rates. These depreciation studies are subject to review and approval by IPL’s and WPL’s respective regulatory commissions. Depreciation expense is included within the recoverable cost of service component of rates collected from customers. The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows: IPL WPL 2025 2024 2023 2025 2024 2023 Electric - generation 3.5 % 3.3 % 3.3 % 3.4 % 3.4 % 3.0 % Electric - distribution 2.9 % 2.8 % 2.8 % 2.7 % 2.7 % 2.7 % Electric - other 3.6 % 5.2 % 5.6 % 4.2 % 6.1 % 6.3 % Gas 3.3 % 3.3 % 3.3 % 2.4 % 2.5 % 2.5 % Other 5.6 % 4.6 % 6.2 % 4.5 % 4.4 % 4.6 % AFUDC - AFUDC represents costs to finance construction additions, including a return on equity component and cost of debt component as required by regulatory accounting. AFUDC for IPL’s construction projects is calculated in accordance with FERC guidelines. AFUDC for WPL’s retail and wholesale jurisdiction construction projects is calculated in accordance with PSCW and FERC guidelines, respectively. The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows: 2025 2024 2023 IPL 7.1 % 7.0 % 7.0 % WPL (retail jurisdiction) 7.4 % 7.4 % 7.4 % WPL (wholesale jurisdiction) 6.6 % 7.1 % 7.1 % In accordance with their respective regulatory commission decisions, IPL applies its AFUDC rates to 100 % of applicable CWIP balances, and WPL generally applies its AFUDC rates to 50 % of applicable CWIP balances and the remaining 50 % of applicable CWIP balances earns a return on such balances as part of its rate base. WPL may be authorized to apply its AFUDC rates to 100 % of the retail portion of the CWIP balances for construction projects requiring a CA or CPCN that were approved by the PSCW after its then most recent rate order. Beginning January 1, 2026, the PSCW also authorized an AFUDC applied to 100% of the retail portion of CWIP balances related to construction activity on capital projects requiring PSCW approval and are impacted by federal law changes. Non-utility and Other Property - General - Non-utility property is recorded at the original cost of acquisition or construction, which includes material, labor and contractor services. Repairs, replacements and renewals of items of property determined to be less than a unit of property or that do not increase the property’s life or functionality are charged to maintenance expense. Upon retirement or sale of non-utility property, the original cost and related accumulated depreciation are removed from the accounts and any gain or loss is included in the income statements. Costs related to software developed or obtained for internal use are capitalized and amortized on a straight-line basis over the estimated useful life of the related software. If software is retired prior to being fully amortized, the remaining book value is recorded as a loss in the income statements. NOTE 1 (f) Revenue Recognition - Utility - Revenues from Alliant Energy’s utility business are primarily from electric and gas sales to customers. Utility revenues are recognized over time as services are rendered or commodities are delivered to customers, and include billed and unbilled components. The billed component is based on the reading of customers’ meters, which occurs on a systematic basis throughout each reporting period and represents the fair value of the services provided or commodities delivered. The unbilled component is recorded at the end of each reporting period based on estimated amounts of energy delivered to customers but not yet billed. IPL and WPL accrue revenues from their wholesale customers to the extent that the actual net revenue requirements calculated in accordance with FERC-approved formula rates for the reporting period are higher or lower than the amounts billed to wholesale customers during such period. Regulatory assets or regulatory liabilities are recorded as the offset for these accrued revenues under formulaic rate-making programs. As of December 31, 2025, the related amounts accrued for IPL and WPL were not material. 69 Table of Contents IPL and WPL participate in bid/offer-based wholesale energy and ancillary services markets operated by MISO. The MISO transactions are grouped together, resulting in a net supply to or net purchase from MISO for each hour of each day. The net supply to MISO is recorded as bulk power sales in “Electric utility revenues” and the net purchase from MISO is recorded in “Electric production fuel and purchased power” in the income statements. Non-utility - Revenues from Alliant Energy’s non-utility businesses are primarily from its Travero business and are recognized over time as services are rendered to customers. Taxes Collected from Customers - Sales or various other taxes collected by certain of Alliant Energy’s subsidiaries on behalf of other agencies are recorded on a net basis and are not included in revenues. Other - Alliant Energy, IPL and WPL do not disclose the value of unsatisfied performance obligations for: (i) contracts with an original expected length of one year or less; and (ii) contracts for which revenue is recognized at the amount to which they have the right to invoice for services performed. NOTE 1 (g) Utility Cost Recovery Mechanisms - Electric Production Fuel and Purchased Power (Fuel-related Costs) - Fuel-related costs are incurred to generate and purchase electricity to meet the demand of IPL’s and WPL’s electric customers. These fuel-related costs include the cost of fossil fuels (primarily natural gas and coal) used to produce electricity at their EGUs, and electricity purchased from MISO wholesale energy markets and under PPAs. These fuel-related costs are recorded in “Electric production fuel and purchased power” in the income statements. IPL Retail - The cost recovery mechanisms for IPL’s retail electric customers provide for monthly adjustments to their electric rates for changes in fuel-related costs. Changes in the under-/over-collection of these costs are recognized in “Electric production fuel and purchased power” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers. WPL Retail - The cost recovery mechanism for WPL’s retail electric customers is based on forecasts of certain fuel-related costs expected to be incurred during forward-looking test periods and fuel monitoring ranges determined by the PSCW during each retail electric rate proceeding or in a separate fuel cost plan approval proceeding. If WPL’s actual fuel-related costs fall outside these fuel monitoring ranges, WPL is authorized to defer the incremental under-/over-collection of fuel-related costs that are outside the approved ranges. Deferral of under-collections are reduced to the extent actual return on common equity earned by WPL during the fuel cost plan year exceeds the most recently authorized return on common equity. Deferred amounts for fuel-related costs outside the approved fuel monitoring ranges are recognized in “Electric production fuel and purchased power” in Alliant Energy’s and WPL’s income statements. The cumulative effects of these deferred amounts are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and WPL’s balance sheets until they are reflected in future billings to customers. IPL and WPL Wholesale - The cost recovery mechanisms for IPL’s and WPL’s wholesale electric customers provide for subsequent adjustments to their electric rates for changes in fuel-related costs. Changes in the under-/over-collection of these costs are recognized in “Electric production fuel and purchased power” in the income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Electric Capacity - PPAs help meet the electricity demand of IPL’s and WPL’s customers. Certain PPAs include minimum payments for IPL’s and WPL’s rights to electric generating capacity, which are charged each period to “Electric production fuel and purchased power” in the income statements. Purchased electric capacity expenses are recovered from IPL’s and WPL’s retail electric customers through changes in base rates determined during periodic rate proceedings. Purchased electric capacity expenses are recovered from IPL’s and WPL’s wholesale electric customers through annual changes in base rates determined by a formula rate structure. Electric capacity revenues are refunded to IPL's retail electric customers through changes in base rates determined during periodic rate proceedings, and to IPL and WPL's wholesale electric customers through annual changes in base rates determined by a formula rate structure. Electric capacity revenues are refunded to WPL's retail electric customers through its fuel cost recovery mechanism. Electric Transmission Service - Costs incurred for the transmission of electricity to meet the demands of IPL’s and WPL’s customers are charged to “Electric transmission service” in the income statements. IPL Retail - Electric transmission service expense is recovered from IPL’s retail electric customers through a transmission cost rider. This cost recovery mechanism provides for periodic adjustments to electric rates charged to retail electric customers for changes in electric transmission service expense. Changes in the under-/over-collection of these costs are recognized in “Electric transmission service” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers. 70 Table of Contents WPL Retail - Electric transmission service expense is recovered from WPL’s retail electric customers through changes in base rates determined during periodic rate proceedings. Pursuant to escrow accounting treatment approved by the PSCW, the difference between actual electric transmission service expense incurred and the amount of electric transmission service costs collected from customers as electric revenues is recognized in “Electric transmission service” in Alliant Energy’s and WPL’s income statements. An offsetting amount is recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and WPL’s balance sheets until reflected in future billings to customers. IPL and WPL Wholesale - IPL and WPL arrange transmission service for the majority of their respective wholesale electric customers. Electric transmission service expense is allocated to and recovered from these customers based on a load ratio share computation. Cost of Gas Sold - Costs are incurred for the purchase, transportation and storage of natural gas to serve IPL’s and WPL’s gas customers and the costs associated with the natural gas delivered to customers are charged to “Cost of gas sold” in the income statements. The tariffs for IPL’s and WPL’s retail gas customers provide for subsequent adjustments to their rates periodically for changes in the cost of gas sold. Changes in the under-/over-collection of these costs are also recognized in “Cost of gas sold” in the income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Energy Efficiency Costs - Costs incurred to fund energy efficiency programs and initiatives that help customers reduce their energy usage are charged to “Other operation and maintenance” in the income statements. Energy efficiency costs incurred by IPL are recovered from its retail electric and gas customers through energy efficiency and demand response cost recovery factor tariffs, which are revised annually and include a reconciliation to eliminate any under-/over-collection of energy efficiency costs from prior periods. Pursuant to escrow accounting treatment approved by the PSCW, the difference between actual energy efficiency costs incurred by WPL and the amount collected from its retail electric and gas customers is recovered through changes in base rates determined during periodic rate proceedings, and reconciliations eliminate any under-/over-collection of energy efficiency costs from prior periods. Changes in the under-/over-collection of energy efficiency costs for IPL and WPL are recognized in “Other operation and maintenance” in the income statements. The cumulative effects of the under-/over-collection of these costs for IPL and WPL are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Renewable Energy Rider - IPL utilized a renewable energy rider prior to its discontinuation on October 1, 2024, effective with the IUC’s order for IPL’s retail electric rate review for the October 2024 through September 2025 Test Period. Prior to October 1, 2024, IPL recovered a return of, as well as earned a return on, its wind generation placed in service in 2019 and 2020 from its retail electric customers through the renewable energy rider. Other applicable costs and tax benefits associated with this wind generation, excluding operation and maintenance expenses, were also included in the rider. This cost recovery mechanism provided for annual adjustments to electric rates charged to IPL’s retail electric customers for actual renewable energy costs and tax benefits. Changes in the under-/over-collection of these costs were recognized in “Electric utility revenue” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs for IPL is recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers. Refer to Note 1(c) for further discussion of the treatment of IPL’s renewable tax credits for rate-making purposes. NOTE 1 (h) Financial Instruments - Financial instruments are periodically used for risk management purposes to mitigate exposures to fluctuations in certain commodity prices, transmission congestion costs and interest rates. The fair value of those financial instruments that are determined to be derivatives are recorded as assets or liabilities on the balance sheets. Certain commodity purchase and sales contracts qualified for and were designated under the normal purchase and sale exception, and were accounted for on the accrual basis of accounting. Alliant Energy, IPL and WPL have elected to not net the fair value amounts of derivatives subject to a master netting arrangement by counterparty. Alliant Energy, IPL and WPL do not offset fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) against fair value amounts recognized for derivative instruments that are executed with the same counterparty under the same master netting arrangement. Refer to Note 2 for discussion of the recognition of regulatory assets and regulatory liabilities related to the unrealized losses and gains on commodity derivative instruments. Refer to Notes 1 4 , 1 5 and 1 6 (f) for further discussion of derivatives and related credit risk. NOTE 1 (i) Asset Impairments - Property, Plant and Equipment of Regulated Operations - Property, plant and equipment of regulated operations are reviewed for possible impairment whenever events or changes in circumstances indicate all or a portion of the carrying value of the assets may be disallowed for rate-making purposes. If IPL or WPL are disallowed recovery of any portion of, or are only allowed a partial return on, the carrying value of their regulated property, plant and equipment that is under construction, has been recently completed or is probable of abandonment, or conclude it is probable recovery or a full return will be disallowed, then an impairment charge is recognized. 71 Table of Contents Property, Plant and Equipment of Non-utility Operations - Property, plant and equipment of non-utility operations are reviewed for possible impairment whenever events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Impairment is indicated if the carrying value of an asset exceeds its undiscounted future cash flows. If an impairment is indicated, a charge is recognized equal to the amount the carrying value exceeds the asset’s fair value. Refer to Note 17 for discussion of an asset valuation charge at Alliant Energy’s non-utility holdings in 2025. Unconsolidated Equity Investments - If events or circumstances indicate the carrying value of investments accounted for under the equity method of accounting exceeds fair value and the decline in value is other than temporary, potential impairment is assessed. If an impairment is indicated, a charge is recognized equal to the amount the carrying value exceeds the investment’s fair value. NOTE 1 (j) Asset Retirement Obligations - The fair value of a legal obligation associated with the retirement of an asset is recorded as a liability when an asset is placed in service, when a legal obligation is subsequently identified or when sufficient information becomes available to determine a reasonable estimate of the fair value of future retirement costs. When an ARO is recorded as a liability, an equivalent amount is added to the asset cost. The fair value of AROs at inception is determined using discounted cash flows analyses. The liability is accreted to its present value and the capitalized cost is depreciated over the useful life of the related asset. Accretion and depreciation expenses related to AROs for IPL’s and WPL’s regulated operations are recorded to regulatory assets on the balance sheets. Revisions in estimated cash flows for IPL’s and WPL’s regulated operations are recorded as an increase or decrease to the ARO liability, with an offset to the asset cost, unless the asset is already retired and then the offset is recorded to regulatory assets or regulatory liabilities on the balance sheets. Upon regulatory approval to recover IPL’s AROs expenditures, its regulatory assets are amortized to depreciation and amortization expenses in Alliant Energy’s and IPL’s income statements over the same time period the ARO expenditures are recovered from IPL’s customers. WPL’s regulatory assets related to AROs are recovered as a component of depreciation rates pursuant to PSCW and FERC orders. Upon settlement of the ARO liability, an entity settles the obligation for its recorded amount or incurs a gain or loss. Any gains or losses related to AROs for IPL’s and WPL’s regulated operations are recorded to regulatory liabilities or regulatory assets on the balance sheets. Refer to Note 13 for details of an ARO charge for steam assets at IPL in 2024. NOTE 1 (k) Debt Issuance and Retirement Costs - Debt issuance costs and debt premiums or discounts are presented on the balance sheets as a direct adjustment to the carrying amount of the related debt liability, and are deferred and amortized over the expected life of each debt issue, considering maturity dates and, if applicable, redemption rights held by us or by others. Alliant Energy’s non-utility businesses and Corporate Services record to interest expense in the period of retirement any unamortized debt issuance costs and debt premiums or discounts on debt retired early. NOTE 1 (l) Current Expected Credit Losses Estimates - Current expected credit losses are estimated for trade and other receivables and credit exposures on guarantees of the performance by third parties. The current expected credit losses for short-term trade receivables are based on estimates of losses resulting from the inability of customers to make required payments. The methodology used to estimate losses is based on historical write-offs, regional economic conditions, significant events that could impact collectability, such as significant weather related matters and related regulatory actions, and actual and forecasted changes to the accounts receivable aging portfolio and write-offs. The current expected credit losses related to guarantees of the performance by third parties are estimated using both quantitative and qualitative information, which utilizes potential outcomes in a range of possible estimated amounts. NOTE 1 (m) Variable Interest Entities - An entity is considered a VIE if its equity investors do not have sufficient equity at risk for the entity to finance its activities without additional subordinated financial support from other parties, the entity is structured with disproportionate voting rights and substantially all of the entity’s activities are conducted on behalf of the investor with disproportionately fewer voting rights, or its equity investors lack any of the following characteristics: (1) power, through voting rights or similar rights, to direct the activities of the entity that most significantly impact the entity’s economic performance; (2) the obligation to absorb expected losses of the entity; or (3) the right to receive expected benefits of the entity. The primary beneficiary of a VIE is required to consolidate the VIE. The financial statements do not reflect any consolidation of VIEs. NOTE 1 (n) Leases - The determination of whether an arrangement qualifies as a lease occurs at the inception of the arrangement. Arrangements that qualify as leases are classified as either operating or finance. Operating and finance lease liabilities represent obligations to make payments arising from the lease. Operating and finance lease assets represent the right to use an underlying asset for the lease term and are recognized at the lease commencement date based on the present value of the lease payments over the lease term. Leases with initial terms less than 12 months are not recognized as leases. For operating leases, an incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. For finance leases, the rate implicit in the lease, if known, is used to determine the present value of the lease payments. If the rate implicit in the lease is not known, the incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. Lease terms include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. Operating lease expense is recognized on a straight-line basis over the expected lease term. Finance lease expense is comprised of depreciation and amortization, and interest expenses. Finance lease assets are accounted for as operating leases for rate-making purposes. 72 Table of Contents NOTE 2. REGULATORY MATTERS Regulatory Assets - Alliant Energy, IPL and WPL assess whether IPL’s and WPL’s regulatory assets are probable of future recovery by considering factors such as applicable regulations, recent orders by the applicable regulatory agencies, historical treatment of similar costs by the applicable regulatory agencies and regulatory environment changes. Based on these assessments, Alliant Energy, IPL and WPL believe the regulatory assets recognized as of December 31, 2025 are probable of future recovery. However, no assurance can be made that IPL and WPL will recover all of these regulatory assets in future rates. If future recovery of a regulatory asset ceases to be probable, the regulatory asset will be charged to expense. At December 31, regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL 2025 2024 2025 2024 2025 2024 Tax-related $ 1,089 $ 989 $ 949 $ 870 $ 140 $ 119 AROs 455 401 312 281 143 120 Pension and OPEB costs 274 315 136 157 138 158 Assets retired early 158 180 149 168 9 12 Non-service pension and OPEB costs 57 51 21 19 36 32 Derivatives 52 60 12 15 40 45 WPL’s Western Wisconsin gas distribution expansion investments 39 42 — — 39 42 Commodity cost recovery 10 68 3 2 7 66 Other 140 168 34 74 106 94 $ 2,274 $ 2,274 $ 1,616 $ 1,586 $ 658 $ 688 At December 31, 2025, IPL and WPL had $ 165 million and $ 28 million, respectively, of regulatory assets that were not earning a return on investment. IPL’s regulatory assets that were not earning a return consisted primarily of the retired Lansing Generating Station, retired analog electric meters, and costs for certain construction projects. WPL’s regulatory assets that were not earning a return consisted primarily of amounts related to the retail portion of under-collected electric transmission service expenses and costs for certain construction projects. The other regulatory assets reported in the above table either earn a return or the cash has not yet been expended, in which case the assets are offset by liabilities that also do not incur a carrying cost. Tax-related - IPL and WPL record regulatory assets for certain temporary differences (primarily related to utility property, plant and equipment at IPL) that result in a decrease in current rates charged to customers and an increase in future rates charged to customers based on the timing of income tax expense that is used to determine such rates. These temporary differences for IPL include the impacts of qualifying deductions for repairs expenditures, allocation of mixed service costs, and Iowa accelerated tax depreciation, which all contribute to lower current income tax expense during the first part of an asset’s useful life and higher current income tax expense during the latter part of an asset’s useful life. Conversely, cost of removal obligations contribute to higher current income tax expense during the first part of an asset’s useful life and lower current income tax expense during the latter part of an asset’s useful life. These regulatory assets will be recovered from customers in the future when these temporary differences reverse resulting in additional current income tax expense used to determine customers’ rates. AROs - Alliant Energy, IPL and WPL believe it is probable that certain differences between expenses accrued for AROs related to their utility operations and expenses recovered currently in rates will be recoverable in future rates, and are deferring the differences as regulatory assets. Refer to Note 13 for discussion of the recognition of additional ARO regulatory assets in 2024, substantially resulting from the enactment of the revised CCR Rule. Pension and other postretirement benefits costs - The IUC, PSCW and FERC have authorized IPL and WPL to record the previously unrecognized net actuarial gains and losses, and prior service costs and credits, as regulatory assets in lieu of accumulated other comprehensive loss on the balance sheets, as these amounts are expected to be recovered in future rates. These regulatory assets will be increased or decreased as the net actuarial gains or losses, and prior service costs or credits, are subsequently amortized and recognized as a component of net periodic benefit costs. Regulatory assets are also increased or decreased as a result of the annual defined benefit plan measurement process. Pension and OPEB costs are included within the recoverable cost of service component of rates charged to IPL’s and WPL’s retail and wholesale customers, which are based upon pension and OPEB costs determined in accordance with GAAP and are calculated in accordance with IPL’s and WPL’s respective regulatory jurisdictions. 73 Table of Contents Assets retired early - IPL and WPL have retired various natural gas- and coal-fired EGUs, and IPL has retired certain analog electric meters. As a result, the remaining net book value of these assets was reclassified from property, plant and equipment to a regulatory asset on their respective balance sheets. Details regarding the recovery of the remaining net book value of these assets from IPL’s and WPL’s customers are as follows (dollars in millions): Entity Asset Retirement Date Regulatory Asset Balance as of Dec. 31, 2025 Recovery Regulatory Approval IPL Lansing 2023 $ 123 Return of (IUC and FERC) and return on (FERC) remaining net book value through 2037 (a) IUC and FERC (b) IPL Analog electric meters 2019 10 Return of remaining net book value through 2028 IUC and FERC IPL Sutherland Units 1 and 3 2017 11 Return of and return on remaining net book value through 2027 (a) IUC and FERC IPL M.L. Kapp Unit 2 2018 5 Return of and return on remaining net book value through 2029 (a) IUC and FERC WPL Edgewater Unit 4 2018 9 Return of and return on remaining net book value through 2028 PSCW and FERC (a) The remaining regulatory asset balances include differences between expected and actual cost of removal obligations. (b) IPL was previously allowed a full recovery of and a full return on the Lansing Generating Station from both its retail and wholesale customers. The IUC’s September 2024 order for IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period includes a return of the remaining net book value of Lansing, but does not include a return on the remaining net book value of Lansing, effective October 1, 2024. As a result, the return on the remaining net book value is no longer recoverable from IPL’s retail electric customers, and a pre-tax non-cash charge of $ 60 million was recorded to “Asset valuation charge for IPL’s Lansing Generating Station” in Alliant Energy’s and IPL’s income statements in 2024, with a corresponding decrease in Alliant Energy’s and IPL’s assets retired early regulatory assets. Non-service pension and OPEB costs - Non-service pension and OPEB costs are recorded to regulatory assets to reflect the impacts of rate-making, and are recovered from IPL’s and WPL’s electric and gas customers through depreciation expense based on the depreciation rates for plant in-service. Derivatives - In accordance with IPL’s and WPL’s fuel and natural gas recovery mechanisms, prudently incurred costs from derivative instruments are recoverable from customers in the future after any losses are realized, and gains from derivative instruments are refundable to customers in the future after any gains are realized. Based on these recovery mechanisms, the changes in the fair value of derivative liabilities/assets resulted in comparable changes to regulatory assets/liabilities on the balance sheets. Refer to Note 14 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during 2025, which resulted in comparable changes to regulatory assets/liabilities on the balance sheets. WPL’s Western Wisconsin gas distribution expansion investments - WPL made contributions in aid of construction to a third party for investments as part of its Western Wisconsin gas distribution expansion project. Pursuant to authorization by the PSCW, Alliant Energy and WPL have recorded a regulatory asset for these costs, and are authorized by the PSCW to recover these amounts from WPL’s retail gas customers in base rates from 2021 through the end of 2040. Commodity cost recovery - Refer to Note 1(g) for details of IPL’s and WPL’s commodity cost recovery mechanisms. The cost recovery mechanism for WPL’s retail electric customers is based on forecasts of certain fuel-related costs expected to be incurred during forward-looking test periods and fuel monitoring ranges determined by the PSCW during each retail electric rate proceeding or in a separate fuel cost plan approval proceeding. In 2022, WPL’s actual fuel-related costs fell outside these fuel monitoring ranges, resulting in a $ 117 million deferral as of December 31, 2022, which WPL substantially collected from October 2023 through December 2025 from its retail electric customers, plus interest ($ 12 million, $ 50 million and $ 52 million was collected in 2023, 2024 and 2025, respectively). In 2023, WPL’s actual fuel-related costs fell outside these fuel monitoring ranges, resulting in a $ 34 million regulatory liability as of December 31, 2023, which was refunded in 2024 to its retail electric customers, plus interest. Regulatory Liabilities - At December 31, regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL 2025 2024 2025 2024 2025 2024 Tax-related $ 690 $ 582 $ 304 $ 286 $ 386 $ 296 Cost of removal obligations 366 347 217 205 149 142 Derivatives 47 53 26 29 21 24 Other 98 46 39 26 59 20 $ 1,201 $ 1,028 $ 586 $ 546 $ 615 $ 482 74 Table of Contents Tax-related regulatory liabilities reduce revenue requirement calculations utilized in IPL’s and WPL’s respective rate proceedings. Cost of removal obligations, to the extent expensed through depreciation rates, reduce rate base. A significant portion of the remaining regulatory liabilities is not used to adjust revenue requirement calculations. Tax-related - Alliant Energy’s, IPL’s and WPL’s tax-related regulatory liabilities are primarily related to excess deferred tax benefits resulting from the remeasurement of accumulated deferred income taxes caused by the Tax Cuts and Jobs Act. The majority of these benefits related to accelerated depreciation are subject to tax normalization rules. These rules limit the rate at which these tax benefits are allowed to be passed on to customers. Additionally, Alliant Energy’s, IPL’s and WPL’s tax-related regulatory liabilities include tax benefits resulting from investment tax credits for IPL’s and WPL’s energy storage facilities and WPL’s Cassville solar facility. Refer to Note 1 (c) for details related to the regulatory treatment of IPL’s and WPL’s investment tax credits. Cost of removal obligations - Alliant Energy, IPL and WPL collect in rates future removal costs for many assets that do not have associated AROs or that have removal costs in addition to AROs. Alliant Energy, IPL and WPL record a regulatory liability for the amounts collected in rates for these future removal costs and reduce the regulatory liability for amounts spent on removal activities. Cash payments related to cost of removal obligations are included in “Other” in cash flows used for investing activities. Rate Reviews - WPL’s Retail Electric and Gas Rate Reviews (2024/2025 Forward-looking Test Period) - In December 2023, the PSCW issued an order authorizing annual base rate increases of $ 49 million and $ 13 million for WPL’s retail electric and gas customers, respectively, effective January 1, 2024, for the 2024 forward-looking Test Period. The PSCW’s order also authorized WPL to implement an additional $ 60 million increase in annual rates for its retail electric customers, effective January 1, 2025, for the 2025 forward-looking Test Period. The key drivers for the annual base rate increases include revenue requirement impacts of increasing electric and gas rate base, including investments in solar generation and energy storage. In addition, the PSCW’s order extended, with certain modifications, an earnings sharing mechanism through the end of 2025. The PSCW also authorized WPL to defer the incremental under-/over-collection of solar and energy storage renewable tax credits that are outside of the approved amounts, which are included in the tax-related lines of the regulatory assets and regulatory liabilities tables above. Refer to Note 3 for discussion of PSCW orders approving deferral of, and the deferral of a return on, incremental solar generation construction costs in 2024 and 2025. WPL’s Retail Electric and Gas Rate Reviews (2026/2027 Forward-looking Test Period) - In December 2025, the PSCW issued an order authorizing annual base rate increases of $ 69 million and $ 7 million for WPL’s retail electric and gas customers, respectively, effective January 1, 2026, for the 2026 forward-looking Test Period. The PSCW’s order also authorized WPL to implement an additional $ 75 million and $ 5 million increase in annual rates for its retail electric and gas customers, respectively, effective January 1, 2027, for the 2027 forward-looking Test Period. IPL’s Retail Electric and Gas Rate Reviews (October 2024 through September 2025 Forward-looking Test Period) - In September 2024, the IUC issued an order authorizing annual base rate increases of $ 185 million for IPL’s retail electric customers, with customers receiving partially offsetting credits for the first 12 months through a tax benefit rider, and $ 10 million for IPL’s retail gas customers, for the October 2024 through September 2025 forward-looking Test Period. Rate changes were effective October 1, 2024. The IUC’s order also reflects the following: • Electric earnings sharing mechanism beginning in calendar year 2025, where IPL would apply excess earnings to the remaining net book value of IPL’s highest earning asset with advance ratemaking principles (currently the Emery Generation Station) based on its authorized return on common equity; • Investment tax credits resulting from renewable generation and energy storage projects may be utilized to offset any revenue deficiency on an annual basis up to IPL’s return on common equity threshold; any remaining investment tax credits, net of the cost of transferability, that are not used to offset any revenue deficiency, will be deferred by IPL and carried forward to offset any revenue deficiency in future years; and • Discontinuation of the renewable energy rider. 75 Table of Contents NOTE 3. PROPERTY, PLANT AND EQUIPMENT At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions): Alliant Energy IPL WPL 2025 2024 2025 2024 2025 2024 Utility: Electric plant: Generation and energy storage in service (a)(b) $ 12,757 $ 11,156 $ 6,251 $ 5,924 $ 6,506 $ 5,232 Distribution in service 8,418 7,811 4,691 4,344 3,727 3,467 Other in service 572 595 369 385 203 210 Anticipated to be retired early (c) — 784 — — — 784 Total electric plant 21,747 20,346 11,311 10,653 10,436 9,693 Gas plant in service 1,938 1,863 1,020 981 918 882 Other plant in service 752 734 456 456 296 278 Accumulated depreciation (c) ( 6,690 ) ( 6,229 ) ( 3,574 ) ( 3,360 ) ( 3,116 ) ( 2,869 ) Net plant 17,747 16,714 9,213 8,730 8,534 7,984 Leased Sheboygan Falls Energy Facility, net (d) — — — — 110 74 Leased land for solar generation, net 190 189 52 53 138 136 Construction work in progress (e) 1,742 1,215 1,166 548 576 667 Other, net 10 5 5 5 5 — Total utility 19,689 18,123 10,436 9,336 9,363 8,861 Non-utility and other: Non-utility Generation, net (f) 146 103 — — — — Corporate Services and other, net (g) 509 475 — — — — Total non-utility and other 655 578 — — — — Total property, plant and equipment $ 20,344 $ 18,701 $ 10,436 $ 9,336 $ 9,363 $ 8,861 (a) Construction costs associated with WPL’s approximately 1,100 MW of new solar generation exceeded the construction cost estimates previously approved by the PSCW by approximately $ 205 million. In 2024, the PSCW issued orders approving deferral of, and the deferral of a return on, the incremental solar generation construction costs in 2024 and 2025. In December 2025, the PSCW issued an order for the 2026/2027 forward-looking Test Period, which includes a full return of and on these solar generation construction costs from WPL’s retail electric customers. As a result, Alliant Energy and WPL concluded that there was not a probable disallowance of the higher rate base amounts as of December 31, 2025. (b) WPL’s Grant County ( 100 MW) and Wood County ( 75 MW) energy storage facilities, and IPL’s Wever ( 99 MW) energy storage facility, were placed in service in 2025. (c) WPL previously received approval from MISO to retire the coal-fired Columbia Units 1 and 2. As of December 31, 2024, WPL planned to cease coal operations at Columbia Units 1 and 2 by the end of 2029, and Alliant Energy and WPL concluded that Columbia Units 1 and 2 met the criteria to be considered probable of abandonment. WPL currently plans to continue coal operations at Columbia Units 1 and 2 at least through 2029 as well as evaluate the potential conversion of Columbia Unit 1 and/or Unit 2 to natural gas. As a result, as of December 31, 2025, Alliant Energy and WPL concluded that Columbia Units 1 and 2 no longer meet the criteria to be considered probable of abandonment. (d) Less accumulated amortization of $ 120 million and $ 116 million for WPL as of December 31, 2025 and 2024, respectively. Refer to Note 9 for discussion of WPL’s remeasurement of this lease in 2025. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and is included in the “Non-utility Generation, net” line within Alliant Energy’s consolidated property, plant and equipment. (e) Alliant Energy’s and IPL’s CWIP balances were higher as of December 31, 2025, compared to December 31, 2024, primarily due to IPL’s energy storage and natural gas-fired generation projects. (f) Less accumulated depreciation of $ 81 million and $ 78 million for Alliant Energy as of December 31, 2025 and 2024, respectively. (g) Less accumulated depreciation of $ 305 million and $ 289 million for Alliant Energy as of December 31, 2025 and 2024, respectively. 76 Table of Contents AFUDC - AFUDC represents costs to finance construction additions, including a return on equity component and cost of debt component as required by regulatory accounting. The concurrent credit for the amount of AFUDC capitalized is recorded as “Allowance for funds used during construction” in the income statements. The amount of AFUDC generated by equity and debt components was as follows (in millions): Alliant Energy IPL WPL 2025 2024 2023 2025 2024 2023 2025 2024 2023 Equity $ 63 $ 54 $ 74 $ 39 $ 31 $ 15 $ 24 $ 23 $ 59 Debt 26 21 26 17 12 6 9 9 20 $ 89 $ 75 $ 100 $ 56 $ 43 $ 21 $ 33 $ 32 $ 79 Non-utility and Other - The non-utility and other property, plant and equipment recorded on Alliant Energy’s balance sheets include the following: Non-utility Generation - The Sheboygan Falls Energy Facility was placed in service in 2005 and is depreciated using the straight-line method over a 45 -year period. Corporate Services and Other - Property, plant and equipment related to Corporate Services include computer software, and the corporate headquarters building located in Madison, Wisconsin. The majority of the software is amortized over a 5 -year period. Other property, plant and equipment include Travero assets (a short-line rail freight service in Iowa; a Mississippi River barge, rail and truck freight terminal in Illinois; and a rail-served warehouse in Iowa). All Corporate Services and Other property, plant and equipment are depreciated using the straight-line method over periods ranging from 5 to 30 years. NOTE 4. JOINTLY-OWNED ELECTRIC UTILITY PLANT Under joint ownership agreements with other utilities, IPL and WPL have undivided ownership interests in jointly-owned EGUs. Each of the respective owners is responsible for the financing of its portion of the construction costs. IPL’s and WPL’s shares of expenses from jointly-owned EGUs are included in the corresponding operating expenses (e.g., electric production fuel, other operation and maintenance, etc.) in the income statements. Information relative to IPL’s and WPL’s ownership interest in these jointly-owned EGUs at December 31, 2025 was as follows (dollars in millions): Ownership Electric Accumulated Provision Construction Interest % Plant for Depreciation Work in Progress IPL Ottumwa Unit 1 48.0 % $ 662 $ 302 $ 7 George Neal Unit 4 25.7 % 201 113 4 George Neal Unit 3 28.0 % 192 89 4 Louisa Unit 1 4.0 % 44 24 1 1,099 528 16 WPL Columbia Units 1-2 and Energy Storage System 53.5 % 868 407 4 West Riverside Energy Center and Solar Facility 56.6 % 456 71 7 Forward Wind Energy Center 42.6 % 118 58 — 1,442 536 11 Alliant Energy $ 2,541 $ 1,064 $ 27 NOTE 5. RECEIVABLES NOTE 5 (a) Accounts Receivable - Details for accounts receivable included on the balance sheets as of December 31 were as follows (in millions): Alliant Energy IPL WPL 2025 2024 2025 2024 2025 2024 Customer $ 139 $ 113 $ — $ — $ 126 $ 98 Unbilled utility revenues 117 101 — — 117 101 Deferred proceeds 126 163 126 163 — — Other 104 58 59 29 39 29 Allowance for expected credit losses ( 10 ) ( 8 ) — — ( 9 ) ( 8 ) $ 476 $ 427 $ 185 $ 192 $ 273 $ 220 77 Table of Contents In 2025, gross write-offs for accounts receivable were as follows (in millions): Originated in 2023 Originated in 2024 Originated in 2025 Alliant Energy $ 1 $ 12 $ 16 IPL 1 8 9 WPL — 4 7 NOTE 5 (b) Sales of Accounts Receivable - IPL maintains a Receivables Agreement whereby it may sell its customer accounts receivables, unbilled revenues and certain other accounts receivables to a third party through wholly-owned and consolidated special purpose entities. In March 2024, IPL amended and extended through March 2026 the purchase commitment from the third party to which it sells its receivables. IPL pays a monthly fee to the third party that varies based on interest rates, limits on cash proceeds and cash amounts received from the third party. Deferred proceeds represent IPL’s interest in the receivables sold to the third party. At IPL’s request, deferred proceeds are paid to IPL from collections of receivables, after paying any required expenses incurred by the third party and the collection agent. Corporate Services acts as collection agent for the third party and receives a fee for collection services. The Receivables Agreement can be terminated by the third party if arrears or write-offs exceed certain levels. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. IPL believes that the allowance for expected credit losses related to its sales of receivables is a reasonable approximation of credit risk of the customers that generated the receivables. Refer to Note 1 5 for discussion of the fair value of deferred proceeds. Under the Receivables Agreement, IPL has the right to receive cash proceeds, up to a certain limit, from the third party in exchange for the receivables sold. The limit on cash proceeds fluctuates between $ 5 million and $ 110 million, which IPL may change periodically throughout the year. As of December 31, 2025, the limit on cash proceeds was $ 110 million and IPL had no available capacity under its sales of accounts receivable program. Cash proceeds are used by IPL to meet short-term financing needs, and cannot exceed the current limit or amount of receivables available for sale, whichever is less. IPL’s maximum and average outstanding aggregate cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program were as follows (in millions): Maximum Average 2025 2024 2023 2025 2024 2023 Outstanding aggregate cash proceeds $ 110 $ 110 $ 110 $ 57 $ 31 $ 51 As of December 31, the attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): 2025 2024 Customer accounts receivable $ 147 $ 137 Unbilled utility revenues 104 108 Receivables sold to third party 251 245 Less: cash proceeds 110 70 Deferred proceeds 141 175 Less: allowance for expected credit losses 15 12 Fair value of deferred proceeds $ 126 $ 163 Outstanding receivables past due $ 21 $ 21 Additional attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): 2025 2024 2023 Collections $ 2,279 $ 2,090 $ 2,233 Write-offs, net of recoveries 12 12 12 NOTE 6. INVESTMENTS Unconsolidated Equity Investments - Alliant Energy’s unconsolidated investments accounted for under the equity method of accounting are as follows (in millions): Ownership Interest at Carrying Value at December 31, Equity (Income) / Loss December 31, 2025 2025 2024 2025 2024 2023 ATC Holdings 16 %, 20 % $ 463 $ 415 ($ 59 ) ($ 57 ) ($ 49 ) Non-utility wind farm in Oklahoma 50 % 112 107 ( 9 ) ( 6 ) ( 7 ) Corporate venture investments Various 76 78 10 3 ( 2 ) Other Various 23 23 ( 2 ) ( 1 ) ( 3 ) $ 674 $ 623 ($ 60 ) ($ 61 ) ($ 61 ) 78 Table of Contents Summary aggregate financial information from the financial statements of these holdings is as follows (in millions): Alliant Energy 2025 2024 2023 Revenues $ 1,080 $ 1,005 $ 898 Operating income 482 433 384 Net income 91 434 370 As of December 31: Current assets 254 223 Non-current assets 10,818 9,930 Current liabilities 879 524 Non-current liabilities 4,243 3,933 Noncontrolling interest 184 221 ATC Holdings - As of December 31, 2025, Alliant Energy has a 16 % ownership interest in ATC and a 20 % ownership interest in ATC Holdco LLC, collectively referred to as ATC Holdings. ATC is an independent, for-profit, transmission-only company. ATC Holdco LLC holds an interest in Duke-American Transmission Company, LLC, which holds a note receivable related to previously owned electric transmission infrastructure in North America. Non-utility Wind Farm in Oklahoma - The non-utility wind farm located in Oklahoma provides electricity to a third-party under a long-term PPA, and has both cash and tax equity ownership. Alliant Energy does not maintain or operate the wind farm, and provided a parent guarantee of its subsidiary’s indemnification obligations under the operating agreement and PPA. Refer to Note 1 6 (d) for discussion of the guarantee. Corporate Venture Investments - Alliant Energy has various minority ownership interests in regional and national venture funds, including a global coalition of energy companies working together to help identify and research innovative technologies and business models within the emerging energy economy. NOTE 7. COMMON EQUITY Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows: 2025 2024 2023 Shares outstanding, January 1 256,690,222 256,096,848 251,134,966 At-the-market offering program — — 4,372,561 Shareowner Direct Plan 360,662 439,107 454,987 Equity-based compensation plans 86,377 154,267 134,334 Shares outstanding, December 31 257,137,261 256,690,222 256,096,848 At December 31, 2025, Alliant Energy had a total of 11 million shares available for issuance in the aggregate, pursuant to its 2020 OIP, Shareowner Direct Plan and 401(k) Savings Plan. At-the-Market Offering Program - In December 2022, Alliant Energy filed a prospectus supplement to sell up to $ 225 million of its common stock through an at-the-market offering program. In 2023, Alliant Energy issued 4,372,561 shares of common stock through this program and received cash proceeds of $ 223 million, net of $ 2 million in commissions and fees. The proceeds from the issuances of common stock were used for general corporate purposes. This at-the-market offering program has expired. In May 2025, Alliant Energy filed a prospectus supplement and executed a related distribution agreement, under which it may sell up to $ 1.3 billion in aggregate of its common stock through 2028 through an at-the-market offering program that includes an equity forward sales component. Alliant Energy expects to use proceeds from the issuance of common stock for general corporate purposes. 79 Table of Contents Alliant Energy entered into forward sale agreements under its at-the-market offering program with various counterparties who, for the quarter and year ended December 31, 2025, borrowed and sold an aggregate of 3,831,429 and 14,595,532 shares of Alliant Energy common stock at an aggregate gross sales price of $ 258 million and $ 944 million, including approximately $ 2 million and $ 7 million in commissions, respectively, to the counterparties payable by Alliant Energy when the forward sale agreements are settled. Alliant Energy has not yet received any proceeds from this program and no amounts have been or will be recorded in equity on Alliant Energy’s balance sheets until the forward sale agreements settle. Alliant Energy currently expects to settle the forward sale agreements in 2026 and 2027 through physical delivery of shares of common stock in exchange for cash proceeds at the then-applicable forward sale price; however, Alliant Energy may elect cash settlement or net share settlement for all or a portion of the obligations under the forward sale agreements. As of December 31, 2025, the weighted-average forward price, net of commissions, was $ 64.44 per share and is subject to daily adjustment based on a floating interest rate factor and decreased by other fixed amounts specified in the forward sale agreements. As of December 31, 2025, Alliant Energy could have settled all of its outstanding forward sale agreements under the at-the-market offering program with physical delivery of 14,595,532 shares of Alliant Energy common stock to the counterparties in exchange for cash of $ 941 million. Alliant Energy has concluded that the forward sale agreements meet the derivative scope exception for certain contracts involving an entity’s own equity. Until settlement of the forward sale agreements, Alliant Energy’s EPS dilution resulting from the agreements, if any, is determined using the treasury stock method. Share dilution occurs when the average market price of Alliant Energy stock during the reporting period is higher than the forward sale price as of the end of the reporting period. As of December 31, 2025, 569,944 incremental shares were included in the calculation of diluted EPS related to the securities under the forward sale agreements. Shareowner Direct Plan - Alliant Energy satisfies its requirements under the Shareowner Direct Plan (dividend reinvestment and stock purchase plan) by acquiring Alliant Energy common stock through original issue, rather than on the open market. NOTE 8. DEBT NOTE 8 (a) Short-term Debt - Alliant Energy and its subsidiaries maintain committed bank lines of credit to provide short-term borrowing flexibility and back-stop liquidity for commercial paper outstanding. At December 31, 2025, the short-term borrowing capacity under a single credit facility agreement, which expires in December 2030, totaled $ 1.3 billion ($ 550 million for Alliant Energy at the parent company level, $ 350 million for IPL and $ 400 million for WPL). Subject to certain conditions, Alliant Energy (at the parent company level), IPL and WPL may each reallocate and change its sublimit up to $ 1 billion, $ 400 million and $ 500 million, respectively, within the $ 1.3 billion total commitment. Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper and borrowings under the single credit facility classified as short-term debt was as follows (dollars in millions): Alliant Energy IPL WPL December 31 2025 2024 2025 2024 2025 2024 Amount outstanding $ 88 $ 558 $ 88 $ 50 $ — $ 183 Weighted average interest rates 3.8 % 4.5 % 3.8 % 4.6 % N/A 4.5 % Available credit facility capacity $ 1,212 $ 742 $ 262 $ 250 $ 400 $ 217 Alliant Energy IPL WPL For the year ended 2025 2024 2025 2024 2025 2024 Maximum amount outstanding (based on daily outstanding balances) $ 741 $ 632 $ 141 $ 80 $ 297 $ 390 Average amount outstanding (based on daily outstanding balances) $ 349 $ 327 $ 25 $ 1 $ 176 $ 70 Weighted average interest rates 4.5 % 5.3 % 4.6 % 5.1 % 4.5 % 5.4 % 80 Table of Contents NOTE 8 (b) Long-Term Debt - Long-term debt, net as of December 31 was as follows (dollars in millions): 2025 2024 Alliant Energy IPL WPL Alliant Energy IPL WPL Senior Debentures (a): 4.1 %, due 2028 $ 500 $ 500 $ — $ 500 $ 500 $ — 3.6 %, due 2029 300 300 — 300 300 — 2.3 %, due 2030 400 400 — 400 400 — 5.7 %, due 2033 300 300 — 300 300 — 6.45 %, due 2033 100 100 — 100 100 — 4.95 %, due 2034 350 350 — 350 350 — 6.3 %, due 2034 125 125 — 125 125 — 5.6 %, due 2035 (b) 600 600 — — — — 6.25 %, due 2039 300 300 — 300 300 — 4.7 %, due 2043 250 250 — 250 250 — 3.7 %, due 2046 300 300 — 300 300 — 3.5 %, due 2049 300 300 — 300 300 — 3.1 %, due 2051 300 300 — 300 300 — 5.45 %, due 2054 300 300 — 300 300 — 5.6 %, due 2055 (b) 300 300 — — — — 3.4 %, (Retired in 2025) — — — 250 250 — 5.5 %, (Retired in 2025) — — — 50 50 — 4,725 4,725 — 4,125 4,125 — Debentures (a): 3.05 %, due 2027 300 — 300 300 — 300 3 %, due 2029 350 — 350 350 — 350 1.95 %, due 2031 300 — 300 300 — 300 3.95 %, due 2032 600 — 600 600 — 600 4.95 %, due 2033 300 — 300 300 — 300 5.375 %, due 2034 300 — 300 300 — 300 6.25 %, due 2034 100 — 100 100 — 100 6.375 %, due 2037 300 — 300 300 — 300 7.6 %, due 2038 250 — 250 250 — 250 4.1 %, due 2044 250 — 250 250 — 250 3.65 %, due 2050 350 — 350 350 — 350 5.7 %, due 2055 (c) 300 — 300 — — — 3,700 — 3,700 3,400 — 3,400 Other: AEF term loan credit agreement through March 2026, 5 % at December 31, 2025 (with Alliant Energy as guarantor) (d) 300 — — — — — AEF 1.4 % senior notes, due 2026 (with Alliant Energy as guarantor) (a) 200 — — 200 — — Alliant Energy 3.875 % convertible senior notes, due 2026 (e) 575 — — 575 — — AEF 5.4 % senior notes, due 2027 (with Alliant Energy as guarantor) (a) 375 — — 375 — — Alliant Energy 3.25 % convertible senior notes, due 2028 (e) 575 — — — — — AEF 4.25 % senior notes, due 2028 (with Alliant Energy as guarantor) (a) 300 — — 300 — — AEF 5.95 % senior notes, due 2029 (with Alliant Energy as guarantor) (a) 300 — — 300 — — AEF 3.6 % senior notes, due 2032 (with Alliant Energy as guarantor) (a) 350 — — 350 — — Alliant Energy 5.75 % junior subordinated notes, due 2056 (f) 725 — — — — — AEF term loan credit agreement, 6 % at December 31, 2024 (with Alliant Energy as guarantor) (Retired in 2025) (d) — — — 300 — — 3,700 — — 2,400 — — Subtotal 12,125 4,725 3,700 9,925 4,125 3,400 Current maturities ( 1,074 ) — — ( 1,171 ) ( 300 ) — Unamortized debt issuance costs ( 70 ) ( 30 ) ( 21 ) ( 55 ) ( 25 ) ( 20 ) Unamortized debt (discount) and premium, net ( 27 ) ( 15 ) ( 10 ) ( 22 ) ( 10 ) ( 10 ) Long-term debt, net (g) $ 10,954 $ 4,680 $ 3,669 $ 8,677 $ 3,790 $ 3,370 81 Table of Contents (a) Contains optional redemption provisions which, if elected by the issuer at its sole discretion, could require material redemption premium payments by the issuer. The redemption premium payments under these optional redemption provisions are variable and dependent on applicable U.S. Treasury rates at the time of redemption. (b) In May 2025, IPL issued $ 600 million of 5.6 % senior debentures due 2035. A portion of the net proceeds was used for the retirement of IPL’s $ 50 million 5.5 % senior debentures and $ 250 million 3.4 % senior debentures. The remainder of the proceeds were used to reduce cash amounts received from its sale of accounts receivable program and commercial paper classified as long-term debt, and for general corporate purposes. In September 2025, IPL issued $ 300 million of 5.6 % senior debentures due 2055. The net proceeds were used to reduce cash amounts received from its sale of accounts receivable program, to reduce outstanding commercial paper, and for general corporate purposes. (c) In December 2025, WPL issued $ 300 million of 5.7 % debentures due 2055. The net proceeds were used to reduce outstanding commercial paper and for general corporate purposes. (d) In March 2025, AEF entered into a $ 300 million variable rate term loan credit agreement, which amended and restated the term loan credit agreement that expired in March 2025, and retired the $ 300 million variable rate term loan set forth therein, which was classified as a non-cash financing activity. AEF’s restated agreement includes an option to increase the amount outstanding with one or more additional term loans in an aggregate amount not to exceed $ 100 million. Refer to Note 14 for information on AEF’s related interest rate swap. In January 2026, AEF retired its $ 300 million term loan. (e) Refer to “ Convertible Senior Notes ” below for additional information. (f) In September 2025, Alliant Energy issued $ 725 million of junior subordinated notes due 2056. The interest rate will reset every 5 years beginning April 1, 2031, to equal the then-current five-year U.S. Treasury rate plus a spread of 2.077 %, provided the interest rate will not reset below 5.75 %. The net proceeds were used to reduce outstanding commercial paper, retire long term debt and for general corporate purposes. Long term debt to be retired includes AEF’s $ 300 million variable rate term loan which was retired in January 2026, AEF’s $ 200 million of 1.4 % senior notes and Alliant Energy’s $ 575 million of 3.875 % convertible senior notes, each of which matures in March 2026 and is expected to be retired at or prior to maturity. Alliant Energy has the option to redeem the notes prior to maturity upon the occurrence of certain events and during specified periods, at redemption prices specified in the governing agreements. (g) There were no significant sinking fund requirements related to the outstanding long-term debt. Convertible Senior Notes 2026 Notes - In March 2023, Alliant Energy issued $ 575 million of 3.875 % convertible senior notes (the 2026 Notes), which are senior unsecured obligations, and used the net proceeds from the issuance for general corporate purposes. The 2026 Notes will mature on March 15, 2026 unless earlier converted or repurchased. Alliant Energy may not redeem the 2026 Notes prior to the maturity date. Holders could have converted their 2026 Notes at their option at any time prior to the close of business on the business day immediately preceding December 15, 2025 only under the following circumstances: • during any calendar quarter commencing after the calendar quarter ending on June 30, 2023 (and only during such calendar quarter), if the last reported sale price of Alliant Energy’s common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter is greater than or equal to 130 % of the conversion price on each applicable trading day during such period; • during the 5 business day period after any 10 consecutive trading day period (the “measurement period”) in which the trading price (as defined in the related Indenture) per $ 1,000 principal amount of 2026 Notes for each trading day of the measurement period was less than 98 % of the product of the last reported sale price of Alliant Energy’s common stock and the conversion rate on each such trading day; or • upon the occurrence of specified corporate events. On or after December 15, 2025 until the close of business on the business day immediately preceding the maturity date, holders may convert all or any portion of their 2026 Notes at any time, regardless of the foregoing circumstances. Upon conversion of the 2026 Notes, Alliant Energy will pay cash up to the aggregate principal amount of the 2026 Notes to be converted and deliver shares of its common stock, in respect of the remainder, if any, of its conversion obligation in excess of the aggregate principal amount of the 2026 Notes being converted. The initial conversion rate is 15.5461 shares of common stock per $ 1,000 principal amount of 2026 Notes (equivalent to an initial conversion price of approximately $ 64.32 per share of Alliant Energy’s common stock). The conversion rate is subject to adjustment in some events but will not be adjusted for any accrued and unpaid interest. In addition, following certain corporate events that occur prior to the maturity date, Alliant Energy will, in certain circumstances, increase the conversion rate for a holder who elects to convert its 2026 Notes in connection with such a corporate event. If Alliant Energy undergoes a fundamental change (as defined in the related Indenture), then, subject to certain conditions, holders of the 2026 Notes may require Alliant Energy to repurchase for cash all or any portion of its 2026 Notes at a fundamental change repurchase price equal to 100 % of the principal amount of the 2026 Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date. 82 Table of Contents As of December 31, 2025 and 2024, the 2026 Notes were classified on Alliant Energy’s balance sheets as “Current maturities of long-term debt”. As of December 31, 2025 and 2024, the net carrying amount of the 2026 Notes was $ 574 million and $ 571 million , with unamortized debt issuance costs of $ 1 million and $ 4 million, and the estimated fair value (Level 2) of the 2026 Notes was $ 599 million and $ 591 million. As of December 31, 2025, there were 407,821 shares of Alliant Energy’s common stock related to the potential conversion of the 2026 Notes included in diluted EPS based on Alliant Energy’s average stock prices and the relevant terms of the 2026 Notes. 2028 Notes - In May 2025, Alliant Energy issued $ 575 million of 3.25 % convertible senior notes (the 2028 Notes), which are senior unsecured obligations, and used the net proceeds from the issuance to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes. The 2028 Notes will mature on May 30, 2028 unless earlier converted or repurchased, and no sinking fund is provided for the 2028 Notes. Alliant Energy may not redeem the 2028 Notes prior to the maturity date. Holders may convert their 2028 Notes at their option at any time prior to the close of business on the business day immediately preceding March 1, 2028 only under the following circumstances: • during any calendar quarter commencing after the calendar quarter ending on September 30, 2025 (and only during such calendar quarter), if the last reported sale price of Alliant Energy’s common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter is greater than or equal to 130 % of the conversion price on each applicable trading day during such period; • during the 5 business day period after any 10 consecutive trading day period (the “measurement period”) in which the trading price (as defined in the related Indenture) per $ 1,000 principal amount of 2028 Notes for each trading day of the measurement period was less than 98 % of the product of the last reported sale price of Alliant Energy’s common stock and the conversion rate on each such trading day; or • upon the occurrence of specified corporate events. O n or after March 1, 2028 until the cl ose of business on the business day immediately preceding the maturity date, holders may convert all or any portion of their 2028 Notes at any time, regardless of the foregoing circumstances. Upon conversion of the 2028 Notes, Alliant Energy will pay cash up to the aggregate principal amount of the 2028 Notes to be converted and pay or deliver, as the case may be, cash, shares of its common stock or a combination of cash and shares of its common stock, at its election, in respect of the remainder, if any, of its conversion obligation in excess of the aggregate principal amount of the 2028 Notes being converted. The initial conversion rate is 13.1773 shares of common stock per $ 1,000 principal amount of 2028 Notes (equivalent to an initial conversion price of approximately $ 75.89 per share of Alliant Energy’s common stock). The conversion rate is subject to adjustment in some events but will not be adjusted for any accrued and unpaid interest. In addition, following certain corporate events that occur prior to the maturity date, Alliant Energy will, in certain circumstances, increase the conversion rate for a holder who elects to convert its 2028 Notes in connection with such a corporate event. If Alliant Energy undergoes a fundamental change (as defined in the related Indenture), then, subject to certain conditions, holders of the 2028 Notes may require Alliant Energy to repurchase for cash all or any portion of its 2028 Notes at a fundamental change repurchase price equal to 100 % of the principal amount of the 2028 Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date. As of December 31, 2025, the conditions allowing holders of the 2028 Notes to convert their 2028 Notes were not met, and the 2028 Notes were classified as “Long-term debt, net” on Alliant Energy’s balance sheet. As of December 31, 2025, the net carrying amount was $ 569 million, with unamortized debt issuance costs of $ 6 million, and the estimated fair value (Level 2) was $ 587 million for the 2028 Notes. As of December 31, 2025, there were no shares of Alliant Energy’s common stock related to the potential conversion of the 2028 Notes included in diluted EPS based on Alliant Energy’s average stock prices and the relevant terms of the 2028 Notes. Five-Year Schedule of Long-term Debt Maturities - At December 31, 2025, long-term debt maturities for 2026 through 2030 were as follows (in millions): 2026 2027 2028 2029 2030 IPL $ — $ — $ 500 $ 300 $ 400 WPL — 300 — 350 — AEF 500 375 300 300 — Alliant Energy parent company 575 — 575 — — Alliant Energy $ 1,075 $ 675 $ 1,375 $ 950 $ 400 Fair Value of Long-term Debt - Refer to Note 1 5 for information on the fair value of long-term debt outstanding. 83 Table of Contents NOTE 9. LEASES Operating Leases - Alliant Energy’s, IPL’s and WPL’s operating leases primarily include leases of space on telecommunication towers and leases of property. Operating lease details are as follows (dollars in millions): December 31, 2025 December 31, 2024 Alliant Energy IPL WPL Alliant Energy IPL WPL Property, plant and equipment, net $ 21 $ 11 $ 9 $ 22 $ 12 $ 9 Other current liabilities $ 2 $ 1 $ 1 $ 2 $ 1 $ 1 Other liabilities 19 10 8 20 11 8 Total operating lease liabilities $ 21 $ 11 $ 9 $ 22 $ 12 $ 9 Weighted average remaining lease term 10 years 10 years 11 years 11 years 11 years 12 years Weighted average discount rate 4 % 4 % 4 % 4 % 4 % 4 % Finance Leases - WPL is currently leasing the Sheboygan Falls Energy Facility from AEF’s Non-utility Generation business. WPL is responsible for the operation of the EGU and has exclusive rights to its output. In 2024, WPL renewed this financing lease through 2044. There are no lease renewal periods remaining. In 2025, WPL’s rent payments increased following the completion of certain enhancements to the Sheboygan Falls Energy Facility, resulting in a lease modification and remeasurement. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and therefore is not reflected in Alliant Energy’s amounts below. Related to their investments in solar generation, IPL and WPL entered into various land lease agreements with unaffiliated parties that have commenced. The leases have various terms with optional renewal periods that are assumed to be extended through the end of the estimated useful lives of the solar generating facilities. The leases do not contain purchase options and are fixed lease payments. Finance lease details are as follows (dollars in millions): December 31, 2025 December 31, 2024 Alliant Energy IPL WPL Alliant Energy IPL WPL Property, plant and equipment, net: Sheboygan Falls Energy Facility N/A N/A $ 110 N/A N/A $ 74 Leased land for solar generation $ 190 $ 52 138 $ 189 $ 53 136 $ 190 $ 52 $ 248 $ 189 $ 53 $ 210 Other current liabilities: Sheboygan Falls Energy Facility N/A N/A $ 4 N/A N/A $ 7 $ — $ — $ 4 $ — $ — $ 7 Other liabilities: Sheboygan Falls Energy Facility N/A N/A $ 106 N/A N/A $ 71 Leased land for solar generation 190 52 138 189 53 136 190 52 244 189 53 207 Total finance lease liabilities $ 190 $ 52 $ 248 $ 189 $ 53 $ 214 Weighted average remaining lease term 30 years 27 years 26 years 31 years 28 years 28 years Weighted average discount rate 5 % 5 % 6 % 5 % 5 % 5 % Alliant Energy IPL WPL 2025 2024 2023 2025 2024 2023 2025 2024 2023 Depreciation and amortization expenses $ — $ — $ 1 $ — $ — $ — $ 2 $ 4 $ 6 Interest expense 9 8 6 3 2 1 11 10 8 Total finance lease expense $ 9 $ 8 $ 7 $ 3 $ 2 $ 1 $ 13 $ 14 $ 14 Finance lease liabilities arising from obtaining leased assets, which represent non-cash financing activities, were as follows (in millions): Alliant Energy IPL WPL 2025 2024 2025 2024 2025 2024 Finance lease liabilities arising from obtaining leased assets $ 1 $ 20 $ — $ 20 $ 39 $ — 84 Table of Contents Expected Maturities - As of December 31, 2025, expected maturities of lease liabilities were as follows (in millions): 2026 2027 2028 2029 2030 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $ 3 $ 3 $ 3 $ 3 $ 2 $ 13 $ 27 $ 6 $ 21 IPL 2 1 1 1 1 8 14 3 11 WPL 1 1 1 1 1 7 12 3 9 Finance Leases: Alliant Energy 9 10 10 10 10 328 377 187 190 IPL 3 3 3 3 3 87 102 50 52 WPL 18 18 19 19 19 386 479 231 248 NOTE 10. REVENUES Revenues from Alliant Energy’s, IPL’s and WPL’s utility businesses are primarily from electric and gas sales provided to customers based on approved tariffs or specific contracts with customers. IPL’s and WPL’s primary performance obligations under such arrangements are to deliver electricity and gas, and their customers simultaneously receive and consume the electricity and gas. For such arrangements, revenues are recognized equivalent to the value of the electricity or gas supplied during each period, including amounts billed during each period and changes in amounts estimated to be billed at the end of each period. IPL and WPL apply the right to invoice method to measure progress towards completing performance obligations to transfer electricity and gas to their customers. IPL provides retail electric and gas service to customers in Iowa, and WPL provides retail and wholesale electric and retail gas service to customers in Wisconsin. IPL also provides electricity to wholesale customers in Illinois and Iowa. IPL’s wholesale power agreement with Southern Minnesota Energy Cooperative expired in July 2025. IPL provided steam from its Prairie Creek Generating Station to high-pressure steam customers in Iowa through 2025. IPL’s and WPL’s retail electric and gas revenues include sales to residential, commercial and industrial customers. IPL’s and WPL’s retail electric and gas customer prices are based on IPL’s and WPL’s cost of service and are determined through general rate review proceedings and various tariff filings with the IUC and PSCW, respectively. Such tariff-based services provide electricity or gas to customers without a defined contractual term. IPL and WPL have wholesale electric market-based rate authority from FERC allowing them to participate in wholesale energy markets (e.g. MISO) and transact directly with third parties. This authority from FERC allows sales of electricity referred to as bulk power sales based on current market values. FERC also allows IPL and WPL to enter into power supply agreements with municipalities and rural electric cooperatives with defined contractual terms, which include standard pricing mechanisms that are detailed in current tariffs accepted by FERC through wholesale rate review proceedings. Revenues from Alliant Energy’s non-utility business customers are primarily from its Travero business, which includes a short-line rail freight service in Iowa; a Mississippi River barge, rail and truck freight terminal in Illinois; freight brokerage services; and a rail-served warehouse in Iowa. 85 Table of Contents Disaggregation of revenues from contracts with customers is provided for each reportable segment (IPL and WPL), as well as by customer class within electric and gas sales, as follows (in millions): Alliant Energy IPL WPL 2025 2024 2023 2025 2024 2023 2025 2024 2023 Electric Utility: Retail - residential $ 1,339 $ 1,236 $ 1,220 $ 661 $ 640 $ 641 $ 678 $ 596 $ 579 Retail - commercial 932 821 820 609 525 519 323 296 301 Retail - industrial 1,034 952 968 531 497 501 503 455 467 Wholesale 184 200 213 39 61 62 145 139 151 Bulk power and other 208 163 124 56 24 38 152 139 86 Total Electric Utility 3,697 3,372 3,345 1,896 1,747 1,761 1,801 1,625 1,584 Gas Utility: Retail - residential 306 275 316 155 148 176 151 127 140 Retail - commercial 153 133 163 72 68 86 81 65 77 Retail - industrial 13 11 16 7 7 11 6 4 5 Transportation/other 53 46 45 31 27 27 22 19 18 Total Gas Utility 525 465 540 265 250 300 260 215 240 Other Utility: Steam 37 40 45 37 40 45 — — — Other utility 14 14 7 10 9 4 4 5 3 Total Other Utility 51 54 52 47 49 49 4 5 3 Non-Utility and Other: Travero and other 89 90 90 — — — — — — Total Non-Utility and Other 89 90 90 — — — — — — Total revenues $ 4,362 $ 3,981 $ 4,027 $ 2,208 $ 2,046 $ 2,110 $ 2,065 $ 1,845 $ 1,827 NOTE 11. INCOME TAXES Income Tax Expense (Benefit) - The components of “Income tax expense (benefit)” in the income statements were as follows (in millions): Alliant Energy IPL WPL 2025 2024 2023 2025 2024 2023 2025 2024 2023 Current tax expense (benefit): Federal $ 10 $ 13 ($ 3 ) ($ 21 ) ($ 19 ) ($ 44 ) $ 38 $ 37 $ 48 State ( 1 ) ( 10 ) ( 6 ) ( 10 ) ( 19 ) ( 21 ) 18 23 25 Deferred tax expense (benefit): Federal 59 60 100 36 38 87 30 24 10 State 33 15 36 2 ( 17 ) 17 16 7 3 Production tax credits ( 208 ) ( 177 ) ( 121 ) ( 133 ) ( 108 ) ( 95 ) ( 75 ) ( 69 ) ( 26 ) Investment tax credits ( 42 ) ( 15 ) ( 1 ) ( 1 ) ( 4 ) ( 1 ) ( 41 ) ( 11 ) — Provision recorded as a change in accrued interest — — ( 1 ) — — ( 1 ) — — — ($ 149 ) ($ 114 ) $ 4 ($ 127 ) ($ 129 ) ($ 58 ) ($ 14 ) $ 11 $ 60 Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income before income taxes. In 2024, Alliant Energy’s and IPL’s effective income tax rates were impacted by the pre-tax non-cash charge of $ 60 million for IPL’s Lansing Generating Station discussed in Note 2 . In the fourth quarter of 2025, Alliant Energy, IPL and WPL retrospectively adopted the Financial Accounting Standards Board’s (FASB) accounting standard for improvements to income tax disclosures. Previously reported information for prior periods has been recast to conform with current period presentation. 86 Table of Contents Alliant Energy 2025 2024 2023 Amount Tax Rate Amount Tax Rate Amount Tax Rate Statutory federal income tax rate $ 139 21 % $ 121 21 % $ 149 21 % State income taxes, net of federal benefits (primarily from state income taxes in Iowa and Wisconsin) 22 3 4 1 21 3 Tax credits: Production tax credits ( 206 ) ( 31 ) ( 171 ) ( 30 ) ( 121 ) ( 17 ) Investment tax credits ( 156 ) ( 24 ) ( 42 ) ( 7 ) ( 3 ) — Research and development credits ( 2 ) — ( 6 ) ( 1 ) — — Tax credit regulatory deferrals (Refer to Note 1 (c) and Note 2 ) 112 17 20 3 2 — Other credits ( 1 ) — — — — — Nontaxable or nondeductible items 4 1 2 — ( 2 ) — Other adjustments: Effect of rate-making on property-related differences (Refer to Note 1(c) and Note 2) ( 37 ) ( 6 ) ( 33 ) ( 6 ) ( 27 ) ( 4 ) Amortization of excess deferred taxes (Refer to Note 2 ) ( 24 ) ( 4 ) ( 13 ) ( 2 ) ( 13 ) ( 2 ) Other — — 4 1 ( 2 ) — Total income tax expense (benefit) and overall income tax rate ($ 149 ) ( 23 %) ($ 114 ) ( 20 %) $ 4 1 % IPL 2025 2024 2023 Amount Tax Rate Amount Tax Rate Amount Tax Rate Statutory federal income tax rate $ 69 21 % $ 49 21 % $ 65 21 % State income taxes, net of federal benefits (primarily from state income taxes in Iowa) ( 10 ) ( 3 ) ( 27 ) ( 12 ) ( 5 ) ( 2 ) Tax credits: Production tax credits ( 133 ) ( 40 ) ( 108 ) ( 46 ) ( 95 ) ( 31 ) Investment tax credits ( 43 ) ( 13 ) ( 8 ) ( 4 ) ( 2 ) ( 1 ) Tax credit regulatory deferrals (Refer to Note 1 (c) and Note 2 ) 42 13 4 1 1 — Other credits ( 1 ) — ( 1 ) — — — Nontaxable or nondeductible items 1 — ( 1 ) — ( 1 ) — Other adjustments: Effect of rate-making on property-related differences (Refer to Note 1(c) and Note 2) ( 30 ) ( 9 ) ( 24 ) ( 10 ) ( 16 ) ( 5 ) Amortization of excess deferred taxes (Refer to Note 2 ) ( 22 ) ( 7 ) ( 13 ) ( 5 ) ( 5 ) ( 1 ) Total income tax expense (benefit) and overall income tax rate ($ 127 ) ( 38 %) ($ 129 ) ( 55 %) ($ 58 ) ( 19 %) 87 Table of Contents WPL 2025 2024 2023 Amount Tax Rate Amount Tax Rate Amount Tax Rate Statutory federal income tax rate $ 81 21 % $ 75 21 % $ 85 21 % State income taxes, net of federal benefits (primarily from state income taxes in Wisconsin) 27 7 23 7 22 5 Tax credits: Production tax credits ( 73 ) ( 19 ) ( 63 ) ( 18 ) ( 26 ) ( 6 ) Investment tax credits ( 114 ) ( 29 ) ( 34 ) ( 10 ) ( 1 ) — Tax credit regulatory deferrals (Refer to Note 1 (c) and Note 2 ) 70 18 17 4 1 — Other credits — — ( 1 ) — — — Nontaxable or nondeductible items 1 — ( 1 ) — ( 2 ) — Other adjustments: Effect of rate-making on property-related differences (Refer to Note 1(c) and Note 2) ( 6 ) ( 2 ) ( 5 ) ( 1 ) ( 12 ) ( 4 ) Amortization of excess deferred taxes (Refer to Note 2 ) — — — — ( 7 ) ( 1 ) Total income tax expense (benefit) and overall income tax rate ($ 14 ) ( 4 %) $ 11 3 % $ 60 15 % Deferred Tax Assets and Liabilities - The deferred tax assets and liabilities included on the balance sheets at December 31 arise from the following temporary differences (in millions): Alliant Energy IPL WPL 2025 2024 2025 2024 2025 2024 Deferred tax liabilities: Property $ 2,828 $ 2,596 $ 1,666 $ 1,521 $ 1,060 $ 999 ATC Holdings 139 135 — — — — Other 167 178 112 120 62 66 Total deferred tax liabilities 3,134 2,909 1,778 1,641 1,122 1,065 Deferred tax assets: Federal credit carryforwards 669 605 455 426 199 166 Net operating losses carryforwards - state 19 20 1 1 — — Other 143 98 48 37 65 34 Subtotal deferred tax assets 831 723 504 464 264 200 Valuation allowances ( 7 ) ( 2 ) ( 4 ) ( 2 ) ( 3 ) — Total deferred tax assets 824 721 500 462 261 200 Total deferred tax liabilities, net $ 2,310 $ 2,188 $ 1,278 $ 1,179 $ 861 $ 865 Carryforwards - At December 31, 2025, carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL State net operating losses 2025-2045 $ 311 $ 7 $ 1 Federal tax credits 2034-2045 669 455 199 State Income Tax Apportionment - Deferred tax assets and liabilities are recorded for temporary differences between the tax basis of assets and liabilities and the amounts reported in the financial statements. Deferred taxes are recorded using currently enacted tax rates and estimates of state income tax apportionment. Estimates of state income tax apportionment are supported by historical data and reasonable projections. Alliant Energy currently expects an increase in total state income tax apportionment primarily due to an increase in projected electric utility revenues driven by demand for energy from commercial and industrial customers, including demand from IPL’s and WPL’s executed electric service agreements with customers who expect to build data centers in their service territories. Alliant Energy parent company’s deferred tax assets were remeasured to reflect an increase in estimated total state income tax apportionment, which resulted in a charge of $ 8 million recorded to income tax expense in Alliant Energy’s income statement and an increase in deferred tax liabilities on Alliant Energy’s balance sheet in 2025. Uncertain Tax Positions - At December 31, 2025, 2024 and 2023, there were no uncertain tax positions or penalties accrued related to uncertain tax positions. As of December 31, 2025, no material changes to unrecognized tax benefits are expected during the next 12 months. 88 Table of Contents Open tax years - Tax years that remain subject to the statute of limitations in the major jurisdictions for each of Alliant Energy, IPL and WPL are as follows: Consolidated federal income tax returns (a) 2022 - 2024 Consolidated Iowa income tax returns (b) 2022 - 2024 Wisconsin combined tax returns (c) 2021 - 2024 (a) The 2022 federal tax return is effectively settled as a result of participation in the IRS Compliance Assurance Program, which allows Alliant Energy and the IRS to work together to resolve issues related to Alliant Energy’s current tax year before filing its federal income tax return. The statute of limitations for these federal tax returns expires three years from each filing date. (b) The statute of limitations for these Iowa tax returns expires three years from each filing date. (c) The statute of limitations for these Wisconsin combined tax returns expires four years from each filing date. Iowa Tax Reform - Pursuant to Iowa tax reform enacted in 2022, annually, and by each November 1, the Iowa Department of Revenue will establish corporate income tax rates for the next tax year based on net corporate income tax receipts for the prior tax year, and reduce such rates if the minimum receipt threshold is met. These corporate income tax rate reductions are currently expected to occur over a period of several years, with a target corporate income tax rate of 5.5 %, compared to the 9.8 % Iowa corporate income tax rate in effect at the time the Iowa tax reform was enacted. In 2023, the Iowa Department of Revenue announced an Iowa corporate income tax rate of 7.1 % effective January 1, 2024. Deferred tax assets and liabilities are measured at the enacted tax rate expected to be applied when temporary differences are to be realized or settled. Given the announcement of the new Iowa corporate income tax rate, Alliant Energy’s and IPL’s deferred tax liabilities were remeasured in 2023 based upon the new rate effective January 1, 2024, which resulted in a $ 74 million reduction of Alliant Energy’s and IPL’s tax-related regulatory assets and a corresponding decrease in their deferred tax liabilities in 2023. In addition, Iowa tax reform made Iowa state income taxes fully deductible for the purpose of determining Iowa state income tax obligations beginning with the 2023 tax year. Alliant Energy reflected the deduction of the additional Iowa state income taxes in its 2023 Iowa state income tax return filed in 2024, which resulted in a $ 26 million reduction of Alliant Energy’s and IPL’s tax-related regulatory assets and a corresponding decrease in their deferred tax liabilities in 2024. The reductions in tax-related regulatory assets are expected to provide cost benefits to IPL’s customers in the future. Alliant Energy parent company’s deferred tax assets were remeasured based upon the new rate effective January 1, 2024, and the deduction of Iowa state income taxes included in Alliant Energy’s 2023 Iowa state income tax return filed in 2024, which resulted in charges of $ 10 million and $ 11 million recorded to income tax expense in Alliant Energy’s income statements and an increase in deferred income tax liabilities on Alliant Energy’s balance sheets in 2023 and 2024, respectively. Alliant Energy is currently unable to predict with certainty the timing or amount of any future rate reductions. NOTE 12. BENEFIT PLANS NOTE 12 (a) Pension and Other Postretirement Benefits Plans - Retirement benefits are provided to substantially all employees through various qualified and non-qualified non-contributory defined benefit pension plans (currently closed to new hires), and/or through defined contribution plans (including 401(k) savings plans). Benefits of the non-contributory defined benefit pension plans are based on the plan participant’s years of service, age and compensation. Benefits of the defined contribution plans are based on the plan participant’s years of service, age, compensation and contributions. Certain defined benefit postretirement health care and life benefits are provided to eligible retirees. In general, the retiree health care plans consist of fixed benefit subsidy structures and the retiree life insurance plans are non-contributory. IPL and WPL account for their participation in Alliant Energy and Corporate Services sponsored plans as multiple-employer plans. For IPL and WPL, amounts below represent the amounts for their plan participants covered under plans they sponsor, as well as amounts directly assigned to them related to certain participants in the Alliant Energy and Corporate Services sponsored plans. Assumptions - The weighted-average assumptions for defined benefit pension and OPEB plans at the measurement date of December 31 were as follows: Defined Benefit Pension Plans OPEB Plans Alliant Energy 2025 2024 2023 2025 2024 2023 Discount rate for benefit obligations 5.52 % 5.65 % 5.36 % 5.40 % 5.62 % 5.40 % Discount rate for net periodic cost 5.65 % 5.36 % 5.54 % 5.62 % 5.40 % 5.53 % Expected rate of return on plan assets 7.60 % 7.73 % 7.80 % 6.37 % 6.22 % 6.50 % Interest crediting rate for Alliant Energy Cash Balance Pension Plan 5.60 % 6.24 % 10.75 % N/A N/A N/A Rate of compensation increase 3.75 % - 4.50 % 3.50 % - 4.50 % 3.30 % - 4.50 % N/A N/A N/A 89 Table of Contents Qualified Defined Benefit Pension Plan OPEB Plans IPL 2025 2024 2023 2025 2024 2023 Discount rate for benefit obligations 5.56 % 5.66 % 5.35 % 5.38 % 5.61 % 5.40 % Discount rate for net periodic cost 5.66 % 5.35 % 5.55 % 5.61 % 5.40 % 5.53 % Expected rate of return on plan assets 7.60 % 7.60 % 7.80 % 6.70 % 6.60 % 6.90 % Rate of compensation increase 4.00 % 3.75 % 3.30 % N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans WPL 2025 2024 2023 2025 2024 2023 Discount rate for benefit obligations 5.56 % 5.66 % 5.35 % 5.38 % 5.61 % 5.40 % Discount rate for net periodic cost 5.66 % 5.35 % 5.54 % 5.61 % 5.40 % 5.53 % Expected rate of return on plan assets 7.60 % 7.80 % 7.80 % 5.75 % 5.61 % 5.65 % Rate of compensation increase 3.75 % 3.50 % 3.30 % N/A N/A N/A Expected rate of return on plan assets - The expected rate of return on plan assets is based on projected asset class returns using target allocations. A forward-looking building blocks approach is used, and historical returns, survey information and capital market information are analyzed to support the expected rate of return on plan assets assumption. Refer to “ Investment Strategy for Plan Assets ” below for additional information related to investment strategy and mix of assets for the pension and OPEB plans. Life Expectancy - The life expectancy assumption is used in determining the benefit obligation and net periodic benefit cost for defined benefit pension and OPEB plans. This assumption utilizes base mortality tables that were released in 2019 by the Society of Actuaries and mortality projection tables that were released in 2021 by the Society of Actuaries. Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans are included below (in millions). The service cost component of net periodic benefit costs is included in “Other operation and maintenance” expenses in the income statements and all other components of net periodic benefit costs are included in “Other (income) and deductions” in the income statements or regulatory assets on the balance sheets. Alliant Energy Defined Benefit Pension Plans OPEB Plans 2025 2024 2023 2025 2024 2023 Service cost $ 4 $ 5 $ 5 $ 1 $ 2 $ 2 Interest cost 46 45 47 8 8 9 Expected return on plan assets (a) ( 53 ) ( 55 ) ( 53 ) ( 4 ) ( 5 ) ( 5 ) Amortization of prior service credit (b) — ( 1 ) ( 1 ) — — — Amortization of actuarial loss (c) 22 24 28 — — 1 $ 19 $ 18 $ 26 $ 5 $ 5 $ 7 IPL Defined Benefit Pension Plans OPEB Plans 2025 2024 2023 2025 2024 2023 Service cost $ 3 $ 3 $ 3 $ 1 $ 1 $ 1 Interest cost 20 20 21 3 3 3 Expected return on plan assets (a) ( 25 ) ( 26 ) ( 26 ) ( 4 ) ( 4 ) ( 3 ) Amortization of actuarial loss (c) 9 9 11 — — 1 $ 7 $ 6 $ 9 $ — $ — $ 2 WPL Defined Benefit Pension Plans OPEB Plans 2025 2024 2023 2025 2024 2023 Service cost $ 1 $ 2 $ 2 $ 1 $ 1 $ 1 Interest cost 20 20 20 3 3 3 Expected return on plan assets (a) ( 23 ) ( 23 ) ( 22 ) ( 1 ) ( 1 ) ( 1 ) Amortization of actuarial loss (c) 11 11 13 — — 1 $ 9 $ 10 $ 13 $ 3 $ 3 $ 4 (a) The expected return on plan assets is based on the expected rate of return on plan assets and the fair value approach to the market-related value of plan assets. (b) Unrecognized prior service credits for the OPEB plans are amortized over the average future service period to full eligibility of the participants of each plan. (c) Unrecognized net actuarial gains or losses in excess of 10% of the greater of the plans’ benefit obligations or assets are amortized over the average future service lives of plan participants, except for the Alliant Energy Cash Balance Pension Plan where gains or losses outside the 10% threshold are amortized over the time period the participants are expected to receive benefits. 90 Table of Contents Benefit Plan Assets and Obligations - A reconciliation of the funded status of qualified and non-qualified defined benefit pension and OPEB plans to the amounts recognized on the balance sheets at December 31 was as follows (in millions): Defined Benefit Pension Plans OPEB Plans Alliant Energy 2025 2024 2025 2024 Change in benefit obligation: Net benefit obligation at January 1 $ 841 $ 876 $ 148 $ 160 Service cost 4 5 1 2 Interest cost 46 45 8 8 Plan participants’ contributions — — 4 3 Actuarial (gain) loss 17 ( 19 ) 6 ( 7 ) Gross benefits paid ( 84 ) ( 66 ) ( 21 ) ( 18 ) Net benefit obligation at December 31 824 841 146 148 Change in plan assets: Fair value of plan assets at January 1 715 732 80 83 Actual return on plan assets 93 38 7 5 Employer contributions 23 11 8 7 Plan participants’ contributions — — 4 3 Gross benefits paid ( 84 ) ( 66 ) ( 21 ) ( 18 ) Fair value of plan assets at December 31 747 715 78 80 Under funded status at December 31 ($ 77 ) ($ 126 ) ($ 68 ) ($ 68 ) Defined Benefit Pension Plans OPEB Plans Alliant Energy 2025 2024 2025 2024 Amounts recognized on the balance sheets consist of: Non-current assets $ — $ — $ 18 $ 17 Current liabilities ( 5 ) ( 3 ) ( 6 ) ( 7 ) Pension and other benefit obligations ( 72 ) ( 123 ) ( 80 ) ( 78 ) Net amounts recognized at December 31 ($ 77 ) ($ 126 ) ($ 68 ) ($ 68 ) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $ 267 $ 312 $ 7 $ 4 Prior service credit ( 1 ) ( 2 ) — — $ 266 $ 310 $ 7 $ 4 Defined Benefit Pension Plans OPEB Plans IPL 2025 2024 2025 2024 Change in benefit obligation: Net benefit obligation at January 1 $ 372 $ 387 $ 59 $ 65 Service cost 3 3 1 1 Interest cost 20 20 3 3 Plan participants’ contributions — — 2 1 Actuarial (gain) loss 6 ( 8 ) 3 ( 3 ) Gross benefits paid ( 38 ) ( 30 ) ( 9 ) ( 8 ) Net benefit obligation at December 31 363 372 59 59 Change in plan assets: Fair value of plan assets at January 1 340 352 59 61 Actual return on plan assets 43 18 6 4 Employer contributions 1 — 2 1 Plan participants’ contributions — — 2 1 Gross benefits paid ( 38 ) ( 30 ) ( 9 ) ( 8 ) Fair value of plan assets at December 31 346 340 60 59 (Under) Over funded status at December 31 ($ 17 ) ($ 32 ) $ 1 $ — 91 Table of Contents Defined Benefit Pension Plans OPEB Plans IPL 2025 2024 2025 2024 Amounts recognized on the balance sheets consist of: Non-current assets $ — $ — $ 14 $ 13 Current liabilities — ( 1 ) ( 1 ) ( 1 ) Pension and other benefit obligations ( 17 ) ( 31 ) ( 12 ) ( 12 ) Net amounts recognized at December 31 ($ 17 ) ($ 32 ) $ 1 $ — Amounts recognized in Regulatory Assets consist of: Net actuarial loss $ 105 $ 126 $ 7 $ 7 Prior service credit — ( 1 ) — — $ 105 $ 125 $ 7 $ 7 Defined Benefit Pension Plans OPEB Plans WPL 2025 2024 2025 2024 Change in benefit obligation: Net benefit obligation at January 1 $ 365 $ 381 $ 56 $ 61 Service cost 1 2 1 1 Interest cost 20 20 3 3 Plan participants’ contributions — — 1 1 Actuarial (gain) loss 9 ( 8 ) 2 ( 3 ) Gross benefits paid ( 33 ) ( 30 ) ( 8 ) ( 7 ) Net benefit obligation at December 31 362 365 55 56 Change in plan assets: Fair value of plan assets at January 1 303 306 13 14 Actual return on plan assets 41 17 2 — Employer contributions 16 10 6 5 Plan participants’ contributions — — 1 1 Gross benefits paid ( 33 ) ( 30 ) ( 8 ) ( 7 ) Fair value of plan assets at December 31 327 303 14 13 Under funded status at December 31 ($ 35 ) ($ 62 ) ($ 41 ) ($ 43 ) Defined Benefit Pension Plans OPEB Plans WPL 2025 2024 2025 2024 Amounts recognized on the balance sheets consist of: Non-current assets $ — $ — $ 4 $ 4 Current liabilities — — ( 5 ) ( 6 ) Pension and other benefit obligations ( 35 ) ( 62 ) ( 40 ) ( 41 ) Net amounts recognized at December 31 ($ 35 ) ($ 62 ) ($ 41 ) ($ 43 ) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $ 115 $ 135 $ 1 $ — Accumulated benefit obligations, aggregate amounts applicable to defined benefit pension and OPEB plans with accumulated benefit obligations in excess of plan assets, as well as defined benefit pension plans with projected benefit obligations in excess of plan assets as of the December 31 measurement date are as follows (in millions): Defined Benefit Pension Plans OPEB Plans Alliant Energy 2025 2024 2025 2024 Accumulated benefit obligations $ 805 $ 824 $ 146 $ 148 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 805 824 146 148 Fair value of plan assets 747 715 78 80 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 824 841 N/A N/A Fair value of plan assets 747 715 N/A N/A 92 Table of Contents Defined Benefit Pension Plans OPEB Plans IPL 2025 2024 2025 2024 Accumulated benefit obligations $ 353 $ 362 $ 59 $ 59 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 353 362 N/A N/A Fair value of plan assets 346 340 N/A N/A Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 363 372 N/A N/A Fair value of plan assets 346 340 N/A N/A Defined Benefit Pension Plans OPEB Plans WPL 2025 2024 2025 2024 Accumulated benefit obligations $ 354 $ 358 $ 55 $ 56 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 354 358 55 56 Fair value of plan assets 327 303 14 13 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 362 365 N/A N/A Fair value of plan assets 327 303 N/A N/A In addition to the amounts recognized in regulatory assets in the above tables for IPL and WPL, regulatory assets were recognized for amounts associated with Corporate Services employees participating in other Alliant Energy sponsored benefit plans that were allocated to IPL and WPL at December 31 as follows (in millions): IPL WPL 2025 2024 2025 2024 Regulatory assets $ 23 $ 25 $ 21 $ 22 Estimated Future Employer Contributions and Benefit Payments - Estimated funding for the qualified and non-qualified defined benefit pension and OPEB plans for 2026 is as follows (in millions): Alliant Energy IPL WPL Defined benefit pension plans (a) $ 23 $ 3 $ 13 OPEB plans 7 1 5 (a) Alliant Energy sponsors several non-qualified defined benefit pension plans that cover certain current and former key employees of IPL and WPL. Alliant Energy allocates pension costs to IPL and WPL for these plans. In addition, IPL and WPL amounts reflect funding for their non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans. Expected benefit payments for the qualified and non-qualified defined benefit plans, which reflect expected future service, as appropriate, are as follows (in millions): Alliant Energy 2026 2027 2028 2029 2030 2031 - 2035 Defined benefit pension benefits $ 75 $ 75 $ 75 $ 74 $ 69 $ 320 OPEB 16 15 15 14 14 61 $ 91 $ 90 $ 90 $ 88 $ 83 $ 381 IPL 2026 2027 2028 2029 2030 2031 - 2035 Defined benefit pension benefits $ 34 $ 33 $ 33 $ 32 $ 32 $ 143 OPEB 6 6 6 6 6 24 $ 40 $ 39 $ 39 $ 38 $ 38 $ 167 WPL 2026 2027 2028 2029 2030 2031 - 2035 Defined benefit pension benefits $ 32 $ 31 $ 31 $ 31 $ 30 $ 142 OPEB 6 6 5 5 5 23 $ 38 $ 37 $ 36 $ 36 $ 35 $ 165 Investment Strategy for Plan Assets - Investment strategies for defined benefit pension and OPEB plan assets combine preservation of principal and prudent risk-taking to protect the integrity of plan assets, in order to meet the obligations to plan participants while minimizing benefit costs over the long term. Investment risk of plan assets is mitigated through an asset mix, which is governed by allocation targets. The asset allocation is monitored regularly, and appropriate steps are taken as needed to rebalance the assets within the prescribed ranges. 93 Table of Contents Defined Benefit Pension Plan Assets - Defined benefit pension plan assets have a long-term investment time horizon and are classified into return-seeking and liability-hedging portfolios. The return-seeking portfolio includes: public equities with different market capitalization, investment style and geography; liquid alternative securities, which include hedge fund strategies; and fixed income investments, which include, but are not limited to, high-yield bonds, emerging market debt, bank loans and private credit bonds. The liability-hedging portfolio includes: fixed-income investments including investment grade instruments of government and corporate issuers, as well as private placements and securitized assets; and fixed income derivative contracts for liability and interest rate hedging positions. At December 31, 2025, the current target ranges and actual allocations for the defined benefit pension plan assets were as follows: Target Range Actual Allocation Allocation Public equity securities 32 % - 44 % 40 % Liquid alternative securities 0 % - 11 % 5 % Return-seeking fixed income securities 4 % - 16 % 7 % Liability-hedging fixed income securities (including cash and equivalents) 41 % - 54 % 48 % Other Postretirement Benefits Plan Assets - OPEB plan assets are comprised of specific assets within certain defined benefit pension plans (401(h) assets) as well as assets held in VEBA trusts. For asset pools with a long-term investment time horizon, investments include public equities with different market capitalization, investment style and geography, and fixed income securities including investment grade instruments of government and corporate issuers. At December 31, 2025, the current target ranges and actual allocations for assets with a long-term investment horizon were as follows: Target Range Actual Allocation Allocation Cash and equivalents 0 % - 5 % 3 % Public equity securities 0 % - 40 % 26 % Fixed income securities 34 % - 100 % 71 % Fair Value Measurements - Fair value measurement accounting establishes three levels of fair value hierarchy that prioritize the inputs to valuation techniques used to measure fair value. Refer to Note 1 5 for discussion of levels within the fair value hierarchy. Level 1 items include investments in securities held in registered investment companies, which are valued at the closing price reported in the active market in which the securities are traded. Level 2 items include cash and equivalents consisting of money market fund investments and cash collateral supporting derivative financial instruments. Certain investments that are measured at fair value using the net asset value practical expedient have not been classified in the fair value hierarchy. These fair value amounts are included below to reconcile the fair value hierarchy to the respective total plan assets. At December 31, the fair values of qualified and non-qualified defined benefit pension plan assets were as follows (in millions): 2025 2024 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $ 71 $ — $ 71 $ — $ 49 $ — $ 49 $ — Assets measured at net asset value 676 667 Due to brokers, net (pending trades with brokers) — ( 1 ) Total pension plan assets $ 747 $ 715 2025 2024 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $ 31 $ — $ 31 $ — $ 21 $ — $ 21 $ — Assets measured at net asset value 315 319 Total pension plan assets $ 346 $ 340 2025 2024 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Cash and equivalents $ 32 $ — $ 32 $ — $ 22 $ — $ 22 $ — Assets measured at net asset value 295 281 Total pension plan assets $ 327 $ 303 94 Table of Contents At December 31, the fair values of OPEB plan assets were as follows (in millions): 2025 2024 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $ 7 $ — $ 7 $ — $ 8 $ — $ 8 $ — Equity securities 19 19 — — 20 20 — — Fixed income securities 52 52 — — 52 52 — — Total OPEB plan assets $ 78 $ 71 $ 7 $ — $ 80 $ 72 $ 8 $ — 2025 2024 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $ 3 $ — $ 3 $ — $ 1 $ — $ 1 $ — Equity securities 17 17 — — 18 18 — — Fixed income securities 40 40 — — 40 40 — — Total OPEB plan assets $ 60 $ 57 $ 3 $ — $ 59 $ 58 $ 1 $ — 2025 2024 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Equity securities $ 2 $ 2 — — $ 2 $ 2 — — Fixed income securities 12 12 — — 11 11 — — Total OPEB plan assets $ 14 $ 14 $ — $ — $ 13 $ 13 $ — $ — For the various defined benefit pension and OPEB plans, Alliant Energy common stock represented less than 1 % of the assets directly held in the plans at December 31, 2025 and 2024, respectively. 401(k) Savings Plans - A significant number of employees participate in defined contribution retirement plans (401(k) savings plans). Alliant Energy common stock directly held by participants represented 7 % of total assets in the 401(k) savings plans at December 31, 2025 and 2024. Costs related to the 401(k) savings plans, which are partially based on the participants’ contributions and include allocated costs associated with Corporate Services employees for IPL and WPL, were as follows (in millions): Alliant Energy IPL WPL 2025 2024 2023 2025 2024 2023 2025 2024 2023 401(k) costs $ 30 $ 31 $ 30 $ 14 $ 14 $ 14 $ 14 $ 15 $ 14 Restructuring and Voluntary Employee Separation Charges - In 2024, Alliant Energy announced restructuring activities, including offering certain employees a voluntary separation package. Approximately 5 % of total Alliant Energy employees accepted the package, and as a result of the restructuring activities, Alliant Energy, IPL and WPL recorded pre-tax charges of $ 29 million, $ 14 million and $ 13 million, respectively, in 2024. These charges were primarily recorded in “Other operation and maintenance” expenses in the income statements. NOTE 12 (b) Equity-based Compensation Plans - In 2020, Alliant Energy’s shareowners approved the 2020 OIP, which permits the grant of shares of Alliant Energy common stock, restricted stock, restricted stock units, performance shares, performance units, and other stock-based or cash-based awards to key employees. At December 31, 2025, performance shares and restricted stock units were outstanding under the 2020 OIP, and 7 million shares of Alliant Energy common stock remained available for grants under the 2020 OIP. Alliant Energy satisfies share payouts related to equity awards through the issuance of new shares of its common stock. Nonvested awards generally do not have non-forfeitable rights to dividends or dividend equivalents when dividends are paid to common shareowners. A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards was as follows (in millions): Alliant Energy IPL WPL 2025 2024 2023 2025 2024 2023 2025 2024 2023 Compensation expense $ 22 $ 12 $ 12 $ 11 $ 6 $ 6 $ 10 $ 5 $ 5 Income tax benefits 3 3 3 2 2 2 1 1 1 As of December 31, 2025, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $ 14 million, $ 7 million and $ 6 million, respectively, which is expected to be recognized over a weighted average period of between one year and two years . Share-based compensation expense is recognized on a straight-line basis over the requisite service periods and is recorded in “Other operation and maintenance” in the income statements. As of December 31, 2025, 725,647 shares were included in the calculation of diluted EPS related to the nonvested equity awards. 95 Table of Contents Performance Shares (Total Shareowner Return Metric) - Payouts of certain performance shares are contingent upon achievement over a three-year period of specified performance criteria, which currently is total shareowner return relative to an investor-owned utility peer group. Performance shares grants are to be paid out in shares of Alliant Energy common stock and are accounted for as equity awards. The fair value of each of these performance shares is based on the fair value of the underlying common stock on the grant date and the probability of satisfying the market condition contained in the agreement during a three-year performance period. The actual number of these performance shares that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200 % of the target number of shares. If minimum performance targets are not met during the performance period, these performance shares are forfeited. Compensation expense is recorded ratably over the performance period based on the fair value of the awards at the grant date. A summary of the performance shares activity, with amounts representing the target number of awards, was as follows: 2025 2024 2023 Shares Weighted Average Grant Date Fair Value Shares Weighted Average Grant Date Fair Value Shares Weighted Average Grant Date Fair Value Nonvested awards, January 1 289,399 $ 51.31 233,954 $ 52.60 190,273 $ 54.13 Granted 105,896 66.52 127,874 46.04 108,712 55.68 Vested — — ( 47,497 ) 46.19 ( 53,431 ) 64.04 Forfeited ( 73,918 ) 54.14 ( 24,932 ) 46.16 ( 11,600 ) 53.88 Nonvested awards, December 31 321,377 55.67 289,399 51.31 233,954 52.60 Restricted Stock Units - Payouts of restricted stock units are based on the expiration of a three-year time-vesting period. Restricted stock unit grants are to be paid out in shares of Alliant Energy common stock and are accounted for as equity awards. The fair value of each of these restricted stock units is based on the closing market price of one share of Alliant Energy common stock on the grant date of the award. Compensation expense is recorded ratably over the performance period based on the fair value of the awards on the grant date. A summary of the restricted stock units activity was as follows: 2025 2024 2023 Units Weighted Average Grant Date Fair Value Units Weighted Average Grant Date Fair Value Units Weighted Average Grant Date Fair Value Nonvested awards, January 1 289,148 $ 51.85 234,259 $ 52.58 198,275 $ 54.53 Granted 102,240 61.73 129,854 48.69 106,124 52.77 Vested ( 63,789 ) 56.70 ( 71,441 ) 48.65 ( 55,345 ) 59.40 Forfeited ( 14,215 ) 51.13 ( 3,524 ) 48.40 ( 14,795 ) 54.53 Nonvested awards, December 31 313,384 54.06 289,148 51.85 234,259 52.58 Performance Shares (Net Income, Environmental and Workforce Composition Metrics) (certain awards formerly granted as Performance Restricted Stock Units) - Payouts of certain performance shares are contingent upon achievement over a three-year period of specific performance criteria, which currently is specified growth of cumulative consolidated net income from continuing operations, as well as environmental and workforce composition metrics. Performance shares grants are to be paid out in shares of Alliant Energy common stock and are accounted for as equity awards. The fair value of each of these performance shares is based on the closing market price of one share of Alliant Energy common stock on the grant date of the award. The actual number of these performance shares that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200 % of the target number of shares under each award type. If minimum performance targets are not met during the performance period, these performance shares are forfeited. Compensation expense is recorded ratably over the performance period based on a probability assessment of payouts for the awards at each reporting period. A summary of the performance shares activity, with amounts representing the target number of awards, was as follows: 2025 2024 2023 Shares Weighted Average Grant Date Fair Value Shares Weighted Average Grant Date Fair Value Shares Weighted Average Grant Date Fair Value Nonvested awards, January 1 330,700 $ 51.81 257,639 $ 52.76 199,874 $ 54.74 Granted 118,883 61.63 146,143 48.55 124,217 52.71 Vested ( 68,233 ) 56.74 ( 67,852 ) 48.66 ( 53,431 ) 59.36 Forfeited ( 16,225 ) 53.05 ( 5,230 ) 48.40 ( 13,021 ) 55.47 Nonvested awards, December 31 365,125 54.03 330,700 51.81 257,639 52.76 96 Table of Contents NOTE 12 (c) Deferred Compensation Plan - Alliant Energy maintains a DCP under which certain key employees may defer up to 80 % of base salary and short-term cash incentive compensation and members of its Board of Directors may elect to defer all or part of their retainer and committee fees. Key employees who have made the maximum allowed contribution to the Alliant Energy 401(k) Savings Plan may receive an additional credit to the DCP. Key employees and Board of Directors members may elect to have their deferrals credited to a company stock account, an interest account, equity accounts or mutual fund accounts based on certain benchmark funds. Company Stock Account - The DCP does not permit reallocation of deferrals credited to the company stock account and all distributions from participants’ company stock accounts are made in the form of shares of Alliant Energy common stock. The deferred compensation obligations for participants’ company stock accounts are recorded in “Additional paid-in capital” and the shares of Alliant Energy common stock held in a rabbi trust to satisfy this obligation are recorded in “Shares in deferred compensation trust” on Alliant Energy’s balance sheets. At December 31, the carrying value of the deferred compensation obligation for the company stock account and the shares in the deferred compensation trust based on the historical value of the shares of Alliant Energy common stock contributed to the rabbi trust, and the fair market value of the shares held in the rabbi trust, were as follows (in millions): 2025 2024 Carrying value $ 14 $ 14 Fair market value 24 22 Interest, Equity and Mutual Fund Accounts - Distributions from participants’ interest, equity and mutual fund accounts are in the form of cash payments. The deferred compensation obligations for participants’ interest, equity and mutual fund accounts are recorded in “Pension and other benefit obligations” on the balance sheets. At December 31, 2025 and 2024, the carrying value of Alliant Energy’s deferred compensation obligations for participants’ interest, equity and mutual fund accounts, which approximates fair market value, was $ 22 million and $ 23 million, respectively. NOTE 13. ASSET RETIREMENT OBLIGATIONS Recognized AROs relate to legal obligations for the removal, closure, dismantlement and management of several assets including, but not limited to, active and inactive ash landfills, ash ponds, wind farms, groundwater, solar facilities, above ground storage tanks and energy storage facilities. Recognized AROs also include legal obligations for the management and final disposition of asbestos and polychlorinated biphenyls. AROs are recorded in “Other current liabilities” and “Other liabilities” on the balance sheets. Refer to Note 2 for information regarding regulatory assets related to AROs. A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions): Alliant Energy IPL WPL 2025 2024 2025 2024 2025 2024 Balance, January 1 $ 663 $ 246 $ 350 $ 148 $ 313 $ 98 Revisions in estimated cash flows ( 1 ) ( 3 ) — ( 1 ) ( 1 ) ( 2 ) Liabilities settled ( 5 ) ( 8 ) ( 2 ) ( 6 ) ( 3 ) ( 2 ) Liabilities incurred (a) 16 409 3 201 13 208 Accretion expense 31 19 16 8 15 11 Balance, December 31 $ 704 $ 663 $ 367 $ 350 $ 337 $ 313 (a) In 2024, substantially due to the enactment of the revised CCR Rule, which significantly expands the scope of regulation to include coal ash ponds at sites that no longer produce electricity and inactive landfills, including some IPL and WPL facilities, Alliant Energy, IPL and WPL initially recorded additional AROs, additional ARO regulatory assets for EGUs no longer in operation, additional property, plant and equipment for EGUs still in operation, and a pre-tax non-cash charge of $ 20 million recorded to “Other operation and maintenance” in Alliant Energy’s and IPL’s income statements for the portion allocated to IPL’s steam business for IPL’s Prairie Creek Generating Station and the retired Sixth Street Generating Station as established in prior rate reviews. The amounts initially recorded in 2024 are expected to be adjusted in the future as additional information is obtained for the specific site closure plans, including the determination of whether or not individual sites are considered legal obligations and the acceptance and approval of compliance approaches, which could change management assumptions and result in a material change to the recorded amounts. NOTE 14. DERIVATIVE INSTRUMENTS Commodity Derivatives - Purpose - Derivative instruments were utilized for risk management purposes to mitigate pricing volatility for fuel used to supply natural gas-fired EGUs, natural gas supplied to retail customers, and purchased electricity, as well as optimize the value of natural gas pipeline capacity and electric generation, which may include swap, physical forward and option contracts. In addition, FTRs help manage transmission congestion costs in the MISO market. Risk policies are maintained that govern the use of such derivative instruments. 97 Table of Contents Notional Amounts - As of December 31, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): Electricity FTRs Natural Gas Diesel Fuel MWhs Years MWhs Years Dths Years Gallons Years 2025 Alliant Energy 1,682 2026 11,332 2026 140,731 2026-2032 — N/A IPL 634 2026 4,482 2026 60,773 2026-2030 — N/A WPL 1,048 2026 6,850 2026 79,958 2026-2032 — N/A 2024 Alliant Energy 1,422 2025-2026 10,232 2025 147,894 2025-2032 2,520 2025 IPL 383 2025-2026 3,551 2025 61,489 2025-2030 — N/A WPL 1,039 2025-2026 6,681 2025 86,405 2025-2032 2,520 2025 Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheet as assets or liabilities. At December 31, based on the maturities of the underlying contracts, the fair values of current derivative assets are included in “Other current assets,” non-current derivative assets are included in “Deferred charges and other,” current derivative liabilities are included in “Other current liabilities” and non-current derivative liabilities are included in “Other liabilities” on the balance sheets as follows (in millions): Alliant Energy IPL WPL 2025 2024 2025 2024 2025 2024 Current derivative assets $ 49 $ 41 $ 33 $ 29 $ 16 $ 12 Non-current derivative assets 20 34 11 19 9 15 Current derivative liabilities 25 26 9 11 16 15 Non-current derivative liabilities 26 32 2 2 24 30 B ased on IPL’s and WPL’s cost recovery mechanisms, the changes in the fair value of derivative liabilities/assets resulted in comparable changes to regulatory assets/liabilities on the balance sheets.