美国联合能源 2025年度报告

FORM 11-K ANNUAL REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year endedDecember31, 2025 or TRANSITION REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from _____________ to _____________ Commission File Number: 1-9894 A.Full title of the plan and address of the plan, if different from that of the issuer named below: B.Name of issuer of the securities held pursuant to the plan and the address of its principal executive office: ALLIANT ENERGY CORPORATION4902 North Biltmore LaneMadison, Wisconsin 53718 REQUIRED INFORMATION The following financial statements and schedules of the Alliant Energy Corporation 401(k) Savings Plan, prepared in accordance withthe financial reporting requirements of the Employee Retirement Income Security Act of 1974, as amended, are filed herewith. ALLIANT ENERGY CORPORATION401(k) SAVINGS PLAN FINANCIAL STATEMENTS AS OF DECEMBER31, 2025 AND 2024AND FOR THE YEAR ENDED DECEMBER31, 2025,SUPPLEMENTAL SCHEDULES AS OF DECEMBER31, 2025, ANDREPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM TABLE OF CONTENTS REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM3FINANCIAL STATEMENTSStatements of Net Assets Available for Benefits as of December31, 2025 and 20244Statement of Changes in Net Assets Available for Benefits for the Year Ended December31, 20255NOTES TO FINANCIAL STATEMENTS1. Description of the Plan62. Summary of Significant Accounting Policies73. Tax Status84. Plan Termination Provisions85. Withdrawals and Distributions86. Fair Value Measurements97. Related Party Transactions and Exempt Parties in Interest Transactions108. Nonexempt Parties in Interest Transactions109. Reconciliation to Form 550010SUPPLEMENTAL SCHEDULESForm 5500, Schedule H, Part IV, line 4a - Schedule of Delinquent Participant Contributions for the year endedDecember31, 202512Form 5500, Schedule H, Part IV, line 4i - Schedule of Assets (Held at End of Year) as of December31, 202513Note: All other schedules required by Section 2520.103-10 of the Department of Labor’s Rules and Regulations forReporting and Disclosure under the Employee Retirement Income Security Act of 1974 have been omitted becausethey are not applicable.SIGNATURES14EXHIBIT INDEX15CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM16 REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM To the Plan Participants and the Plan Administrator of Alliant Energy Corporation 401(k) Savings Plan Opinion on the Financial Statements We have audited the accompanying statements of net assets available for benefits of the Alliant Energy Corporation 401(k) SavingsPlan (the "Plan") as of December 31, 2025 and 2024, the related statement of changes in net assets available for benefits for the yearended December 31, 2025, and the related notes (collectively referred to as the "financial statements"). In our opinion, the financialstatements present fairly, in all material respects, the net assets available for benefits of the Plan as of December 31, 2025 and 2024,and the changes in net assets available for benefits for the year ended December 31, 2025, in conformity with accounting principlesgenerally accepted in the United States of America. Basis for Opinion These financial statements are the responsibility of the Plan's management. Our responsibility is to express an opinion on the Plan'sfinancial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting OversightBoard (United States) (PCAOB) and are required to be independent with respect to the Plan in accordance with the U.S. federalsecurities 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 auditto 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 erroror fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidenceregarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles usedand significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believethat our audits provide a reasonable basis for our opinion. Report on Supplemental Schedules The supplemental schedules of assets (held at end of year) as of December31, 2025 and of delinquent participant contributions for theyear ended December 31, 2025 have been subjected to audit procedures performed in conjunction with the audit of the Plan's financialstatements. The supplemental schedules are the responsibility of