ALLIANT ENERGY CORP 10-K

ITEM 9A. CONTROLS AND PROCEDURES Alliant Energy’s, IPL’s and WPL’s management evaluated, with the participation of each of Alliant Energy’s, IPL’s and WPL’s Chief Executive Officer, Chief Financial Officer and Disclosure Committee, the effectiveness of the design and operation of Alliant Energy’s, IPL’s and WPL’s disclosure controls and procedures (as defined in Rule 13a-15(e) of the Securities Exchange Act of 1934, as amended) as of December 31, 2025 pursuant to the requirements of the Securities Exchange Act of 1934, as amended. Based on their evaluation, the Chief Executive Officer and the Chief Financial Officer concluded that Alliant Energy’s, IPL’s and WPL’s disclosure controls and procedures were effective as of the quarter ended December 31, 2025. There was no change in Alliant Energy’s, IPL’s and WPL’s internal control over financial reporting that occurred during the quarter ended December 31, 2025 that has materially affected, or is reasonably likely to materially affect, Alliant Energy’s, IPL’s or WPL’s internal control over financial reporting. Management’s Annual Report on Internal Control over Financial Reporting - The management of Alliant Energy, IPL and WPL are responsible for establishing and maintaining adequate internal control over financial reporting, as such term is defined in Rules 13a-15(f) and 15d-15(f) under the Securities Exchange Act of 1934, as amended. Alliant Energy’s, IPL’s and WPL’s internal control over financial reporting is designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with GAAP. Because of the inherent limitations of internal control over financial reporting, misstatements may not be prevented or detected on a timely basis. Also, projections of any evaluation of the effectiveness of the internal control over financial reporting to future periods are subject to the risk that the controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate. Alliant Energy’s, IPL’s and WPL’s management assessed the effectiveness of their respective internal control over financial reporting as of December 31, 2025 using the criteria set forth in Internal Control - Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission. Based on these assessments, Alliant Energy’s, IPL’s and WPL’s management concluded that, as of December 31, 2025, their respective internal control over financial reporting was effective. Deloitte & Touche LLP, Alliant Energy’s independent registered public accounting firm, has audited Alliant Energy’s internal control over financial reporting. That report is included herein. This report does not include an attestation report of IPL’s and WPL’s independent registered public accounting firm regarding its assessment of IPL’s and WPL’s internal control over financial reporting. 107 Table of Contents REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM To the Shareowners and the Board of Directors of Alliant Energy Corporation: Opinion on Internal Control over Financial Reporting We have audited the internal control over financial reporting of Alliant Energy Corporation and subsidiaries (the “Company”) 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 (COSO). In our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of December 31, 2025, based on criteria established in Internal Control - Integrated Framework (2013) issued by COSO. We have also audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (PCAOB), the consolidated financial statements as of and for the year ended December 31, 2025, of the Company and our report dated February 20, 2026, expressed an unqualified opinion on the Company’s 2025 financial statements. Basis for Opinion The Company’s management is responsible for maintaining effective internal control over financial reporting and for its assessment of the effectiveness of internal control over financial reporting, included in the accompanying Management’s Annual Report on Internal Control over Financial Reporting. Our responsibility is to express an opinion on the Company’s internal control over financial reporting based on our audit. 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 audit in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether effective internal control over financial reporting was maintained in all material respects. Our audit included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, testing and evaluating the design and operating effectiveness of internal control based on the assessed risk, and performing such other procedures as we considered necessary in the circumstances. We believe that our audit provides a reasonable basis for our opinion. Definition and Limitations of Internal Control over Financial Reporting A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (1) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (2) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (3) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements. Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate. /s/ Deloitte & Touche LLP Milwaukee, Wisconsin February 20, 2026 108 Table of Contents ITEM 9B. OTHER INFORMATION During the quarter ended December 31, 2025, no director or officer of Alliant Energy, IPL or WPL adopted or terminated a Rule 10b5-1 trading arrangement or non-Rule 10b5-1 trading arrangement, as each term is defined in Item 408(a) of Regulation S-K . ITEM 9C. DISCLOSURE REGARDING FOREIGN JURISDICTIONS THAT PREVENT INSPECTIONS None. PART III ITEM 10. DIRECTORS, EXECUTIVE OFFICERS AND CORPORATE GOVERNANCE The information required by Item 10 relating to directors and nominees for election of directors at the 2026 Annual Meeting of Shareowners, the timely filing of reports under Section 16 of the Securities Exchange Act of 1934, audit committees and audit committee financial experts, insider trading policies and procedures, and Alliant Energy’s Code of Conduct is incorporated herein by reference to the relevant information in the 2026 Alliant Energy Proxy Statement, which will be filed with the SEC within 120 days after the end of Alliant Energy’s fiscal year. Information regarding executive officers of Alliant Energy may be found in Part I of this report under the caption “ Information About Executive Officers .” IPL and WPL are omitted pursuant to Instruction I(2)(c). ITEM 11. EXECUTIVE COMPENSATION The information required by Item 11 for Alliant Energy is incorporated herein by reference to the relevant information in the 2026 Alliant Energy Proxy Statement, which will be filed with the SEC within 120 days after the end of Alliant Energy’s fiscal year. IPL and WPL are omitted pursuant to Instruction I(2)(c). ITEM 12. SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT AND RELATED STOCKHOLDER MATTERS Information regarding Alliant Energy’s equity compensation plans as of December 31, 2025 was as follows: (A) (B) (C) Number of securities to be Weighted-average Number of securities remaining available issued upon exercise of exercise price of for future issuance under equity outstanding options, outstanding options, compensation plans (excluding Plan Category warrants and rights warrants and rights securities reflected in column (A)) Equity compensation plans approved by shareowners 1,686,388 (a) N/A (b) 6,785,563 (c) Equity compensation plans not approved by shareowners (d) N/A N/A N/A (e) 1,686,388 N/A 6,785,563 (a) Represents performance shares and restricted stock units granted under the 2020 OIP, all of which are paid out in shares of Alliant Energy’s common stock. The performance share awards reflect an assumed payout at the maximum performance multiplier of 200%. The restricted stock units vest at the expiration of a three-year time-vesting period. (b) No cash consideration is received when shares are distributed for earned performance shares and restricted stock units. Accordingly, there is no weighted-average exercise price. (c) All of the available shares under the 2020 OIP may be issued as awards in the form of shares of Alliant Energy’s common stock, restricted stock, restricted stock units, performance shares, performance units and other stock-based or cash-based awards. As of December 31, 2025, there were performance shares and restricted stock units outstanding under the 2020 OIP, the only plan under which such equity awards are currently granted. (d) As of December 31, 2025, there were 367,338 shares of Alliant Energy’s common stock held under the DCP, which is described in Note 1 2 (c) . (e) There is no limit on the number of shares of Alliant Energy’s common stock that may be held under the DCP. The remainder of the information required by Item 12 for Alliant Energy is incorporated herein by reference to the relevant information in the 2026 Alliant Energy Proxy Statement, which will be filed with the SEC within 120 days after the end of Alliant Energy’s fiscal year. IPL and WPL are omitted pursuant to Instruction I(2)(c). 109 Table of Contents ITEM 13. CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS, AND DIRECTOR INDEPENDENCE The information required by Item 13 for Alliant Energy is incorporated herein by reference to the relevant information in the 2026 Alliant Energy Proxy Statement, which will be filed with the SEC within 120 days after the end of Alliant Energy’s fiscal year. IPL and WPL are omitted pursuant to Instruction I(2)(c). ITEM 14. PRINCIPAL ACCOUNTING FEES AND SERVICES ALLIANT ENERGY The information required by Item 14 is incorporated herein by reference to the relevant information in the 2026 Alliant Energy Proxy Statement, which will be filed with the SEC within 120 days after the end of Alliant Energy’s fiscal year. IPL AND WPL Each of IPL’s and WPL’s Audit Committee of the Board of Directors has adopted a policy that requires advance approval of all audit, audit-related, tax and other permitted services performed by the independent registered public accounting firm. The policy provides for pre-approval by the Audit Committee of specifically defined audit and non-audit services after the Audit Committee is provided with the appropriate level of details regarding the specific services to be provided. The policy does not permit delegation of the Audit Committee’s authority to management. In the event the need for specific services arises between Audit Committee meetings, the Audit Committee has delegated to the Chairperson of the Audit Committee authority to approve permitted services provided that the Chairperson reports any decisions to the Audit Committee at its next scheduled meeting. The principal accounting fees billed to Alliant Energy by its independent registered public accounting firm, all of which were approved in advance by the Audit Committee, directly related and allocated to IPL and WPL were as follows (in thousands): IPL WPL 2025 2024 2025 2024 Fees % of Total Fees % of Total Fees % of Total Fees % of Total Audit fees $1,479 96% $1,412 96% $1,294 90% $1,242 92% Audit-related fees 61 4% 59 4% 137 10% 103 8% Tax fees 4 —% 3 —% 4 —% 3 —% All other fees 2 —% 3 —% 2 —% 2 —% $1,546 100% $1,477 100% $1,437 100% $1,350 100% IPL’s and WPL’s audit fees for 2025 and 2024 consisted of the respective fees billed for the audits of the financial statements of IPL and its subsidiaries and WPL and its subsidiaries, for reviews of financial statements included in Form 10-Q filings, and for services normally provided in connection with statutory and regulatory filings, such as financing transactions. IPL’s and WPL’s audit fees also included their respective portion of fees for the 2025 and 2024 audits of Alliant Energy’s financial statements and effectiveness of internal controls over financial reporting. IPL’s and WPL’s audit-related fees for 2025 and 2024 consisted of the fees billed for services rendered related to employee benefits plan audits, other attest services and WPL’s audit-related fees for 2025 also included an audit of expenditures of federal awards for the Department of Energy. IPL’s and WPL’s tax fees for 2025 and 2024 consisted of the fees billed for professional services rendered for tax compliance. All other fees for 2025 and 2024 for IPL and WPL consisted of license fees for accounting research software products and seminars. The Audit Committee does not consider the provision of non-audit services by the independent registered public accounting firm described above to be incompatible with maintaining independence of the independent registered public accounting firm. PART IV ITEM 15. EXHIBITS, FINANCIAL STATEMENT SCHEDULES (1) Consolidated Financial Statements - Refer to Item 8 Financial Statements and Supplementary Data for Alliant Energy’s, IPL’s and WPL’s financial statements and Reports of Independent Registered Public Accounting Firm (Public Company Accounting Oversight Board ID No. 34 ). 110 Table of Contents (2) Financial Statement Schedules - SCHEDULE I - CONDENSED PARENT COMPANY FINANCIAL STATEMENTS ALLIANT ENERGY CORPORATION (Parent Company Only) Year Ended December 31, CONDENSED STATEMENTS OF INCOME 2025 2024 2023 (in millions) Operating expenses $ 4 $ 3 $ 3 Operating loss ( 4 ) ( 3 ) ( 3 ) Other (income) and deductions: Equity earnings from consolidated subsidiaries ( 863 ) ( 734 ) ( 742 ) Interest expense 57 40 34 Other ( 3 ) 5 4 Total other (income) and deductions ( 809 ) ( 689 ) ( 704 ) Income before income taxes 805 686 701 Income tax benefit ( 6 ) ( 3 ) ( 5 ) Net income $ 811 $ 689 $ 706 Refer to accompanying Notes to Condensed Financial Statements. ALLIANT ENERGY CORPORATION (Parent Company Only) December 31, CONDENSED BALANCE SHEETS 2025 2024 (in millions) ASSETS Current assets: Cash and cash equivalents $ 512 $ — Notes receivable from affiliated companies 114 103 Income tax refunds receivable 12 12 Other 6 2 Total current assets 644 117 Investments: Investments in consolidated subsidiaries 9,784 9,123 Other 1 1 Total investments 9,785 9,124 Other assets 102 84 Total assets $ 10,531 $ 9,325 LIABILITIES AND EQUITY Current liabilities: Current maturities of long-term debt $ 574 $ 571 Commercial paper — 325 Notes payable to affiliated companies 1,300 1,401 Other 21 10 Total current liabilities 1,895 2,307 Long-term debt, net (excluding current portion) 1,286 — Other liabilities 4 3 Common equity: Common stock and additional paid-in capital 3,104 3,063 Retained earnings 4,255 3,965 Accumulated other comprehensive income 1 1 Shares in deferred compensation trust ( 14 ) ( 14 ) Total common equity 7,346 7,015 Total liabilities and equity $ 10,531 $ 9,325 Refer to accompanying Notes to Condensed Financial Statements. 111 Table of Contents ALLIANT ENERGY CORPORATION (Parent Company Only) Year Ended December 31, CONDENSED STATEMENTS OF CASH FLOWS 2025 2024 2023 (in millions) Net cash flows from operating activities $ 529 $ 355 $ 445 Cash flows used for investing activities: Capital contributions to consolidated subsidiaries ( 365 ) ( 380 ) ( 325 ) Net change in notes receivable from and payable to affiliates ( 113 ) 326 ( 281 ) Net cash flows used for investing activities ( 478 ) ( 54 ) ( 606 ) Cash flows from (used for) 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 1,286 — 565 Net change in commercial paper ( 325 ) 168 ( 195 ) Other ( 2 ) — 1 Net cash flows from (used for) financing activities 461 ( 301 ) 161 Net increase (decrease) in cash, cash equivalents and restricted cash 512 — — Cash, cash equivalents and restricted cash at beginning of period — — — Cash, cash equivalents and restricted cash at end of period $ 512 $ — $ — Supplemental cash flows information: Cash (paid) received during the period for: Interest ($ 45 ) ($ 40 ) ($ 27 ) Income taxes, net: Federal $ 4 $ 11 $ 8 State - Iowa — ( 15 ) ( 13 ) State - Wisconsin — 12 27 Total income taxes, net $ 4 $ 8 $ 22 Refer to accompanying Notes to Condensed Financial Statements. ALLIANT ENERGY CORPORATION (Parent Company Only) NOTES TO CONDENSED FINANCIAL STATEMENTS Pursuant to rules and regulations of the SEC, the Condensed Financial Statements of Alliant Energy Corporation (Parent Company Only) do not reflect all of the information and notes normally included with financial statements prepared in accordance with GAAP. Therefore, these Condensed Financial Statements should be read in conjunction with the Financial Statements and related Notes included in the combined 2025 Form 10-K, Part II, Item 8 , which is incorporated herein by reference. In the Condensed Financial Statements of Alliant Energy Corporation (Parent Company Only), investments in subsidiaries are accounted for using the equity method. NOTE: All other schedules are omitted because they are not applicable or not required, or because that required information is shown either in the financial statements or in the notes thereto. (3) Exhibits Required by SEC Regulation S-K - Pursuant to Item 601(b)(4)(iii) of Regulation S-K, the registrants agree to furnish to the SEC, upon request, any instrument defining the rights of holders of unregistered long-term debt not filed as an exhibit to this combined Form 10-K. No such instrument authorizes securities in excess of 10% of the total assets of Alliant Energy, IPL or WPL, as the case may be. The following exhibits for Alliant Energy, IPL and WPL are filed herewith or incorporated herein by reference. Exhibit Number Description 3.1 Restated Articles of Incorporation of Alliant Energy, as amended (incorporated by reference to Exhibit 4.1 to Alliant Energy’s Registration Statement on Form S-8 (Reg. No. 333-117654)) 3.1a Articles of Amendment to Restated Articles of Incorporation of Alliant Energy, as amended, effective May 4, 2016 (incorporated by reference to Exhibit 3.1 to Alliant Energy’s Form 10-Q for the quarter ended March 31, 2016 (File No. 1-9894)) 3.2 Amended and Restated Bylaws of Alliant Energy, effective November 8, 2022 (incorporated by reference to Exhibit 3.1 to Alliant Energy’s Form 10-Q for the quarter ended September 30, 2022 (File No. 1-9894)) 3.3 Amended and Restated Articles of Incorporation of WPL, effective May 9, 2013 (incorporated by reference to Exhibit 3.4 to WPL’s Form 8-K, filed May 13, 2013 (File No. 0-337)) 3.4 Amended and Restated Bylaws of WPL, effective October 27, 2020 (incorporated by reference to Exhibit 3.3 to WPL’s Form 8-K, filed October 29, 2020 (File No. 0-337)) 112 Table of Contents Exhibit Number Description 3.5 Amended and Restated Articles of Incorporation of IPL, effective December 20, 2021 (incorporated by reference to Exhibit 3.1 to IPL’s Form 8-K, filed December 21, 2021 (File No. 1-4117)) 3.6 Amended and Restated Bylaws of IPL, effective October 27, 2020 (incorporated by reference to Exhibit 3.2 to IPL’s Form 8-K, filed October 29, 2020 (File No. 1-4117)) 4.1 Amended and Restated Five-Year Master Credit Agreement, effective December 17, 2021 , among Alliant Energy, IPL, WPL, Wells Fargo Bank, National Association (N.A.) and the lender parties set forth therein (incorporated by reference to Exhibit 4.1 to Alliant Energy’s Form 8-K, filed December 21, 20 21 (File No. 1-9894)) 4.1a First Amendment to Amended and Restated Five-Year Master Credit Agreement, effective March 15, 2023, among Alliant Energy, IPL, WPL, Wells Fargo Bank, N ational A ssociat ion and the lender parties set forth therein (incorporated by reference to Exhibit 4.1 to Alliant Energy’s Form 10 - Q for the quarter ended March 31, 202 3 (File No. 1-9894)) 4.1b Second Amendment to Amended and Restated Five-Year Master Credit Agreement, effective December 18, 2024, among Alliant Energy, IPL, WPL, Wells Fargo Bank, N atio nal A s sociation and the lender parties set forth therein (incorporated by reference to Exhibit 4.1 to Alliant Energy’s Form 8-K filed December 18, 2024 (File No. 1-9894)) 4.1c Extension and Third Amendment to Amended and Restated Five-Year Master Credit Agreement, effective December 18, 2025, among Alliant Energy, IPL, WPL, Wells Fargo Bank, National Association and the lender parties set forth therein 4.2 Indenture, dated as of March 2, 2023, between Alliant Energy and The Bank of New York Mellon Trust Company, N.A., as trustee (incorporated by reference to Exhibit 4.1 to Alliant Energy's Form 8-K, filed March 3, 2023 (File No. 1-9894)) 4.3 Indenture, dated as of May 15, 2025, between Alliant Energy and The Bank of New York Mellon Trust Company, N.A., as trustee (incorporated by reference to Exhibit 4.1 to Alliant Energy’s Form 8-K, filed May 15, 2025 (File No. 1-9894)) 4.4 Indenture, dated as of September 26, 2025, between Alliant Energy and The Bank of New York Mellon Trust Company, N.A., as trustee (incorporated by reference to Exhibit 4.1 to Alliant Energy’s Form 8-K, filed September 26, 2025 (File No. 1-9894)) 4.4a First Supplemental Indenture, dated as of September 26, 2025, between Alliant Energy and The Bank of New York Mellon Trust Company, N.A., as trustee, relating to the 5.750% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2056 (incorporated by reference to Exhibit 4.2 to Alliant Energy’s Form 8-K, filed September 26, 2025 (File No. 1-9894)) 4.5 Indenture, dated as of June 12, 2018, among AEF, Alliant Energy, as guarantor, and The Bank of New York Mellon Trust Company, N.A., as trustee (incorporated by reference to Exhibit 4.1 to Alliant Energy’s Form 8-K, filed June 12, 2018 (File No. 1-9894)) 4.6 Indenture, dated as of November 20, 2020, among AEF, Alliant Energy as guarantor, and The Bank of New York Mellon Trust Company, N.A., as trustee (incorporated by reference to Exhibit 4.1 to Alliant Energy’s Form 8-K, filed November 23, 2020 (File No. 1-9894) 4.7 Indenture, dated as of February 28, 2022, among AEF, Alliant Energy, as guarantor, and The Bank of New York Mellon Trust Company, N.A., as trustee (incorporated by reference to Exhibit 4.1 to Alliant Energy’s Form 8-K, filed March 1, 2022 (File No. 1-9894)) 4.8 Indenture, dated as of November 10, 2023, among AEF, Alliant Energy, as guarantor, and The Bank of New York Mellon Trust Company, N.A., as trustee (incorporated by reference to Exhibit 4.1 to Alliant Energy's Form 8-K, filed November 13, 2023 (File No. 1-9894)) 4.9 Indenture, dated as of June 6, 2024, among AEF, Alliant Energy, as guarantor, and The Bank of New York Mellon Trust Company, N.A., as trustee (incorporated by reference to Exhibit 4.1 to Alliant Energy ’ s Form 8-K, filed June 6, 2024 (File No. 1-9894)) 4.10 Indenture, dated as of June 20, 1997, between WPL and U.S. Bank Trust Company, N. A., Successor, as Trustee (incorporated by reference to Exhibit 4.33 to Amendment No. 2 to WPL’s Registration Statement on Form S-3 (Reg. No. 033-60917)) 4.10a First Supplemental Indenture, dated September 16, 2021, among WPL, Wells Fargo Bank, National Association, as Original Trustee, and U.S. Bank National Association, as Series Trustee (incorporated by reference to Exhibit 4.1 to WPL's Form 8-K, filed September 16, 2021 (File No. 0-337)) 4.11 Officers’ Certificate, dated as of July 28, 2004, creating WPL’s 6.25% Debentures due July 31, 2034 (incorporated by reference to Exhibit 4.1 to WPL’s Form 8-K, filed August 2, 2004 (File No. 0-337)) 4.12 Officers’ Certificate, dated as of August 8, 2007, creating WPL’s 6.375% Debentures due August 15, 2037 (incorporated by reference to Exhibit 4.1 to WPL’s Form 8-K, filed August 9, 2007 (File No. 0-337)) 4.13 Officer s ’ Certificate, dated as of October 1, 2008, creating WPL’s 7.60% Debentures due October 1, 2038 (incorporated by reference to Exhibit 4.2 to WPL’s Form 8-K, filed October 2, 2008 (File No. 0-337)) 4.14 Officers’ Certificate, dated as of October 14, 2014, creating WPL’s 4.10% Debentures due October 15, 2044 (incorporated by reference to Exhibit 4.1 to WPL’s Form 8-K, filed October 14, 2014 (File No. 0-337)) 4.15 Officers’ Certificate, dated as of October 10, 2017, creating WPL’s 3.05% Debentures due October 15, 2027 (incorporated by reference to Exhibit 4.1 to WPL’s Form 8-K, filed October 10, 2017 (File No. 0-337)) 4.16 Officers’ Certificate, dated as of June 24, 2019, creating WPL’s 3.00% Debentures due July 1, 2029 (incorporated by reference to Exhibit 4.1 to WPL’s Form 8-K, filed June 24, 2019 (File No. 0-337)) 4.17 Officers’ Certificate, dated as of April 2, 2020, creating WPL’s 3.65% Debentures due April 1, 2050 (incorporated by reference to Exhibit 4.1 to WPL’s Form 8-K, filed April 2, 2020 (File No. 0-337)) 4.18 Officers’ Certificate, dated as of August 15, 2022, creating WPL’s 3.950% Debentures due September 1, 2032 (incorporated by reference to Exhibit 4.1 to WPL’s Form 8-K, filed August 15, 2022 (File No. 0-337)) 4.19 Officers’ Certificate, dated as of March 30, 2023, creating WPL's 4.950% Debentures due April 1, 2033 (incorporated by reference to Exhibit 4.1 to WPL's Form 8-K, filed March 30, 2023 (File No. 0-337)) 4.20 Officers’ Certificate, dated as of March 7, 2024, creating WPL’s 5.375% Debentures due March 30, 2034 (incorporated by reference to Exhibit 4.1 to WPL’s Form 8-K, filed March 7, 2024 (File No. 0-337)) 113 Table of Contents Exhibit Number Description 4.21 Officers’ Certificate, dated December 5, 2025, creating WPL’s 5.700% Debentures due 2055 (incorporated by reference to Exhibit 4.1 to WPL’s Form 8-K, filed December 5, 2025 (File No. 0-337)) 4.22 Indenture (For Senior Unsecured Debt Securities), dated as of August 20, 2003, between IPL and The Bank of New York Mellon Trust Co., N.A. (f/k/a The Bank of New York Trust Co., N.A.), as Trustee (incorporated by reference to Exhibit 4.11 to IPL’s Registration Statement on Form S-3 (Reg. No. 333-108199)) 4.23 Officer’s Certificate, dated as of October 14, 2003, creating IPL’s 6.45% Senior Debentures due October 15, 2033 (incorporated by reference to Exhibit 4.1 to IPL’s Form 8-K, filed October 15, 2003 (File No. 1-4117)) 4.24 Officer’s Certificate, dated as of May 3, 2004, creating IPL’s 6.30% Senior Debentures due May 1, 2034 (incorporated by reference to Exhibit 4.1 to IPL’s Form 8-K, filed May 5, 2004 (File No. 1-4117)) 4.24a Officer’s Certificate, dated as of August 2, 2004, reopening IPL’s 6.30% Senior Debentures due May 1, 2034 (incorporated by reference to Exhibit 4.1 to IPL’s Form 8-K, filed August 5, 2004 (File No. 1-4117)) 4.25 Officer’s Certificate, dated as of July 7, 2009, creating IPL’s 6.25% Senior Debentures due July 15, 2039 (incorporated by reference to Exhibit 4.1 to IPL’s Form 8-K, filed July 8, 2009 (File No. 1-4117)) 4.26 Officer’s Certificate, dated as of October 8, 2013, creating IPL’s 4.70% Senior Debentures due October 15, 2043 (incorporated by reference to Exhibit 4.1 to IPL’s Form 8-K, filed October 8, 2013 (File No. 1-4117)) 4.27 Officer’s Certificate, dated as of September 15, 2016, creating IPL’s 3.70% Senior Debentures due September 15, 2046 (incorporated by reference to Exhibit 4.1 to IPL’s Form 8-K, filed September 15, 2016 (File No. 1-4117)) 4.28 Officer’s Certificate, dated as of September 26, 2018, creating IPL’s 4.10% Senior Debentures due September 26, 2028 (incorporated by reference to Exhibit 4.1 to IPL’s Form 8-K, filed September 26, 2018 (File No. 1-4117)) 4.29 Officer’s Certificate, dated as of April 1, 2019, creating IPL’s 3.60% Senior Debentures due April 1, 2029 (incorporated by reference to Exhibit 4.1 to IPL’s Form 8-K, filed April 1, 2019 (File No. 1-4117)) 4.30 Officer’s Certificate, dated as of September 26, 2019, creating IPL’s 3.50% Senior Debentures due September 30, 2049 (incorporated by reference to Exhibit 4.1 to IPL’s Form 8-K, filed September 26, 2019 (File No. 1-4117)) 4.31 Officer’s Certificate, dated as of June 2, 2020, creating IPL’s 2.3% Senior Debentures due June 1, 2030 (incorporated by reference to Exhibit 4.1 to IPL’s Form 8-K, filed June 2, 2020 (File No. 1-4117)) 4.32 Officer’s Certificate, dated as of November 19, 2021, creating IPL’s 3.1% Senior Debentures due November 30, 2051 (incorporated by reference to Exhibit 4.1 to IPL’s Form 8-K, filed November 19, 2021 (File No. 1-4117)) 4.33 Officer’s Certificate, dated as of September 21, 2023, creating IPL’s 5.70% Senior Debentures due October 15, 2033 (incorporated by reference to Exhibit 4.1 to IPL’s Form 8-K, filed September 21, 2023 (File No. 1-4117)) 4.34 Officer’s Certificate, dated as of September 6, 2024, creating IPL’s 4.950% Senior Debentures due September 30, 2034 and IPL’s 5.450% Senior Debentures due September 30, 2054 (incorporated by reference to Exhibit 4.1 to IPL’s Form 8-K, filed September 6, 2024 (File No. 1-4117)) 4.35 Officer’s Certificate, dated as of May 19, 2025, creating IPL’s 5.600% Senior Debentures due June 29, 2035 (incorporated by reference to Exhibit 4.1 to IPL’s Form 8-K, filed May 19, 2025 (File No. 1-4117)) 4.36 Officer’s Certificate, dated as of September 11, 2025, creating IPL’s 5.600% Senior Debentures due October 1, 2055 (incorporated by reference to Exhibit 4.1 to IPL’s Form 8-K, filed September 11, 2025 (File No. 1-4117)) 4.37 Description of Common Stock of Alliant Energy (incorporated by reference to Exhibit 4.32 to Alliant Energy ’ s Form 10-K for the year 2023 (File No. 1-9894)) 10.1 Second Amended and Restated Term Loan Credit Agreement, dated as of March 3, 2025, among AEF, Alliant Energy, U.S. Bank National Association and the lender parties set forth therein (incorporated by reference to Exhibit 10.1 to Alliant Energy’s Form 8-K, filed March 3, 2025 (File No. 1-9894)) 10.2# 2020 O I P (incorporated by reference to Appendix A to Alliant Energy’s definitive proxy statement filed on Schedule 14A on April 9, 2020 (File No. 1-9894)) 10.2a# Form of Performance Share Agreement pursuant to the 2020 OIP, amended in 2022 (incorporated by reference to Exhibit 10.3d to Alliant Energy’s Form 10-K for the year 2021 (File No. 1-9894)) 10.2b# Form of Restricted Stock Unit Agreement pursuant to the 2020 OIP, amended in 2022 (incorporated by reference to Exhibit 10.3e to Alliant Energy’s Form 10-K for the year 2021 (File No. 1-9894)) 10.2c# Form of Performance Restricted Stock Unit Agreement (Workforce Composition Metric) pursuant to the 2020 OIP, amended in 2022 (incorporated by reference to Exhibit 10.3f to Alliant Energy’s Form 10-K for the year 2021 (File No. 1-9894)) 10.2d# Form of Performance Restricted Stock Unit Agreement (Net Income Metric) pursuant to the 2020 OIP, amended in 2022 (incorporated by reference to Exhibit 10.3g to Alliant Energy’s Form 10-K for the year 2021 (File No. 1-9894)) 10.2e# Form of Performance Share Agreement pursuant to the 2020 OIP, amended in 2024 (incorporated by reference to Exhibit 10.2h to Alliant Energy’s Form 10-K for the year 2023 (File No. 1-9894)) 10.2f# Form of Performance Share Agreement pursuant to the 2020 OIP, amended in 2025 (incorporated by reference to Exhibit 10.2f to Alliant Energy's Form 10-K for the year 2024 (File No. 1-9894)) 10.2g# Form of Restricted Stock Unit Agreement pursuant to the 2020 OIP, amended in 2025 (incorporated by reference to Exhibit 10.2g to Alliant Energy's Form 10-K for the year 2024 (File No. 1-9894)) 10.3# DCP, as amended and restated effective November 1, 2024 (incorporated by reference to Exhibit 10.3 to Alliant Energy's Form 10-K for the year 2024 (File No. 1-9894)) 10.4# Alliant Energy Rabbi Trust Agreement for DCPs (incorporated by reference to Exhibit 10.19 to Alliant Energy’s Form 10-K for the year 2005 (File No. 1-9894)) 10.4a# Amendment to the Alliant Energy Rabbi Trust Agreement for DCPs (incorporated by reference to Exhibit 10.2 to Alliant Energy’s Form 10-Q for the quarter ended June 30, 2015 (File No. 1-9894)) 114 Table of Contents Exhibit Number Description 10.4b# Second Amendment to the Alliant Energy Rabbi Trust Agreement for DCPs (incorporated by reference to Exhibit 10.3 to Alliant Energy’s Form 10-Q for the quarter ended June 30, 2015 (File No. 1-9894)) 10.5# Alliant Energy Excess Retirement Plan (incorporated by reference to Exhibit 10.1 to Alliant Energy’s Form 10-Q for the quarter ended September 30, 2008 (File No. 1-9894)) 10.5a# Amendment to the Alliant Energy Excess Retirement Plan (incorporated by reference to Exhibit 10.4 to Alliant Energy’s Form 8-K, filed December 5, 2011 (File No. 1-9894)) 10.6# Form of Key Executive Employment and Severance Agreement (KEESA), by and between Alliant Energy and L.M. Barton (incorporated by reference to Exhibit 10.1 to Alliant Energy’s Form 8-K, filed October 28, 2021 (File No. 1-9894)) 10.7# Form of KEESA, by and between Alliant Energy and each of R.J. Durian, D.A. de Leon, M.N. Farlinger, R. Sundararajan, A.P. Smyth and R.C. Valcq (incorporated by reference to Exhibit 10.2 to Alliant Energy’s Form 8-K, filed October 28, 2021 (File No. 1-9894)) 10.8# Executive Officer Severance Benefit Plan, as amended and restated, effective October 29, 2018 (incorporated by reference to Exhibit 10.1 to Alliant Energy’s Form 10-Q for the quarter ended September 30, 2018 (File No. 1-9894)) 10.9# Terms of Alliant Energy Executive Short-term Incentive Plan (incorporated by reference to Exhibit 10.11 to Alliant Energy's Form 10-K for the year 2024 (File No. 1-9894)) 10.10# Form of Sign-On Bonus Reimbursement Agreement (incorporated by reference to Exhibit 10.14 to Alliant Energy ’ s Form 10-K for the year 2022 (File No . 1-9894)) 10.11# Form of Relocation Reimbursement Agreement (incorporated by reference to Exhibit 10.13 to Alliant Energy ’ s Form 10-K for the year 2023 (File No. 1-9894)) 10.12# Summary of Compensation and Benefits for Non-Employee Directors of Alliant Energy, IPL and WPL, effective January 1, 2026 19 Alliant Energy Insider Trading Policies and Procedures (incorporated by reference to Exhibit 19 to Alliant Energy’s Form 10-K for the year 2024 (File No. 1-9894)) 21.1 Subsidiaries of Alliant Energy 23.1 Consent of Independent Registered Public Accounting Firm for Alliant Energy 23.2 Consent of Independent Registered Public Accounting Firm for IPL 23.3 Consent of Independent Registered Public Accounting Firm for WPL 31.1 Certification of the Chief Executive Officer for Alliant Energy 31.2 Certification of the Chief Financial Officer for Alliant Energy 31.3 Certification of the Chief Executive Officer for IPL 31.4 Certification of the Chief Financial Officer for IPL 31.5 Certification of the Chief Executive Officer for WPL 31.6 Certification of the Chief Financial Officer for WPL 32.1 Written Statement of the Chief Executive Officer and Chief Financial Officer Pursuant to 18 U.S.C.§1350 for Alliant Energy 32.2 Written Statement of the Chief Executive Officer and Chief Financial Officer Pursuant to 18 U.S.C.§1350 for IPL 32.3 Written Statement of the Chief Executive Officer and Chief Financial Officer Pursuant to 18 U.S.C.§1350 for WPL 97 Alliant Energy Incentive Compensation Recovery Policy (incorporated by reference to Exhibit 97 to Alliant Energy’s Form 10-K for the year ended 2023 (File No. 1-9894)) 101.INS Inline XBRL Instance Document - the instance document does not appear in the Interactive Data File because its XBRL tags are embedded within the Inline XBRL document 101.SCH Inline XBRL Taxonomy Extension Schema Document 101.CAL Inline XBRL Taxonomy Extension Calculation Linkbase Document 101.LAB Inline XBRL Taxonomy Extension Label Linkbase Document 101.PRE Inline XBRL Taxonomy Extension Presentation Linkbase Document 101.DEF Inline XBRL Taxonomy Extension Definition Linkbase Document 104 Cover Page Interactive Data File (embedded within the Inline XBRL document) # A management contract or compensatory plan or arrangement. ITEM 16. FORM 10-K SUMMARY None. 115 Table of Contents SIGNATURES Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the Registrants have duly caused this report to be signed on their behalf by the undersigned, thereunto duly authorized on the 20th day of February 2026. ALLIANT ENERGY INTERSTATE POWER WISCONSIN POWER CORPORATION AND LIGHT COMPANY AND LIGHT COMPANY By: /s/ Lisa M. Barton By: /s/ Lisa M. Barton By: /s/ Lisa M. Barton Lisa M. Barton Lisa M. Barton Lisa M. Barton President and Chief Executive Officer Chief Executive Officer Chief Executive Officer Pursuant to the requirements of the Securities Exchange Act of 1934, this report has been signed below by the following persons on behalf of the Registrants and in the capacities indicated on the 20th day of February 2026. ALLIANT ENERGY INTERSTATE POWER WISCONSIN POWER CORPORATION AND LIGHT COMPANY AND LIGHT COMPANY /s/ Lisa M. Barton /s/ Lisa M. Barton /s/ Lisa M. Barton Lisa M. Barton Lisa M. Barton Lisa M. Barton President, Chief Executive Officer and Director (Principal Executive Officer) Chief Executive Officer and Director (Principal Executive Officer) Chief Executive Officer and Director (Principal Executive Officer) /s/ Robert J. Durian /s/ Robert J. Durian /s/ Robert J. Durian Robert J. Durian Robert J. Durian Robert J. Durian Executive Vice President and Chief Financial Officer (Principal Financial Officer) Executive Vice President and Chief Financial Officer (Principal Financial Officer) Executive Vice President and Chief Financial Officer (Principal Financial Officer) /s/ Dylan M. Syse /s/ Dylan M. Syse /s/ Dylan M. Syse Dylan M. Syse Dylan M. Syse Dylan M. Syse Chief Accounting Officer and Controller (Principal Accounting Officer) Chief Accounting Officer and Controller (Principal Accounting Officer) Chief Accounting Officer and Controller (Principal Accounting Officer) /s/ Patrick E. Allen /s/ Patrick E. Allen /s/ Patrick E. Allen Patrick E. Allen, Board Chair and Director Patrick E. Allen, Board Chair and Director Patrick E. Allen, Board Chair and Director /s/ Ignacio A. Cortina /s/ Ignacio A. Cortina /s/ Ignacio A. Cortina Ignacio A. Cortina, Director Ignacio A. Cortina, Director Ignacio A. Cortina, Director /s/ Stephanie L. Cox /s/ Stephanie L. Cox /s/ Stephanie L. Cox Stephanie L. Cox, Director Stephanie L. Cox, Director Stephanie L. Cox, Director /s/ N. Joy Falotico /s/ N. Joy Falotico /s/ N. Joy Falotico N. Joy Falotico, Director N. Joy Falotico, Director N. Joy Falotico, Director /s/ Michael D. Garcia /s/ Michael D. Garcia /s/ Michael D. Garcia Michael D. Garcia, Director Michael D. Garcia, Director Michael D. Garcia, Director /s/ Roger K. Newport /s/ Roger K. Newport /s/ Roger K. Newport Roger K. Newport, Director Roger K. Newport, Director Roger K. Newport, Director /s/ Thomas F. O’Toole /s/ Thomas F. O’Toole /s/ Thomas F. O’Toole Thomas F. O’Toole, Director Thomas F. O’Toole, Director Thomas F. O’Toole, Director /s/ Christie Raymond /s/ Christie Raymond /s/ Christie Raymond Christie Raymond, Director Christie Raymond, Director Christie Raymond, Director /s/ Carol P. Sanders /s/ Carol P. Sanders /s/ Carol P. Sanders Carol P. Sanders, Director Carol P. Sanders, Director Carol P. Sanders, Director 116