Alliant Energy Files 8-K on Corporate Structure

TL;DR

Alliant Energy's subsidiary Interstate Power & Light filed an 8-K detailing historical corporate name changes and structure.

AI Summary

Alliant Energy Corp. (through its subsidiary Interstate Power & Light Co.) filed an 8-K on September 11, 2025, reporting other events and financial statements. The filing details changes in company structure and historical name changes, including Interstate Energy Corp. and WPL Holdings Inc. becoming Alliant Energy Corp., and IES Utilities Inc. becoming Interstate Power & Light Co.

Why It Matters

This filing provides clarity on the corporate lineage and structure of Alliant Energy and its subsidiary, which is important for understanding the entity's history and regulatory standing.

Risk Assessment

Risk Level: low — The filing primarily concerns historical corporate information and does not appear to involve new financial risks or operational changes.

Key Players & Entities

• INTERSTATE POWER & LIGHT CO (company) — Filer and subsidiary
• ALLIANT ENERGY CORP (company) — Parent company
• INTERSTATE ENERGY CORP (company) — Former company name
• WPL HOLDINGS INC (company) — Former company name
• IES UTILITIES INC (company) — Former company name

FAQ

Key Financial Figures

• $0.01 — liant Energy Corporation, Common Stock, $0.01 Par Value LNT Nasdaq Global Select Mar
• $300 million — terms and conditions set forth therein, $300 million aggregate principal amount of IPL's 5.6

Filing Documents

• lnt-20250908.htm (8-K) — 35KB
• lnt090820258-kex11.htm (EX-1.1) — 337KB
• lnt090820258-kex41.htm (EX-4.1) — 56KB
• lnt090820258-kex51.htm (EX-5.1) — 43KB
• lnt090820258-kex52.htm (EX-5.2) — 15KB
• lnt090820258-kex991.htm (EX-99.1) — 8KB
• exhibit9911a.jpg (GRAPHIC) — 18KB
• header.jpg (GRAPHIC) — 3KB
• simmons.jpg (GRAPHIC) — 36KB
• 0000352541-25-000074.txt ( ) — 801KB
• lnt-20250908.xsd (EX-101.SCH) — 3KB
• lnt-20250908_def.xml (EX-101.DEF) — 14KB
• lnt-20250908_lab.xml (EX-101.LAB) — 26KB
• lnt-20250908_pre.xml (EX-101.PRE) — 15KB
• lnt-20250908_htm.xml (XML) — 4KB

01 Other Events

Item 8.01 Other Events. On September 8, 2025, Interstate Power and Light Company ("IPL"), a subsidiary of Alliant Energy Corporation, entered into an Underwriting Agreement (the "Underwriting Agreement") with KeyBanc Capital Markets Inc., PNC Capital Markets LLC, TD Securities (USA) LLC, and U.S. Bancorp Investments, Inc., as representatives of the several underwriters listed therein (the "Underwriters"), pursuant to which IPL agreed to sell, and the Underwriters agreed to purchase, subject to the terms and conditions set forth therein, $300 million aggregate principal amount of IPL's 5.600% Senior Debentures due 2055 (the "Debentures"), in a public offering (the "Offering"). The Debentures are to be issued under an Indenture dated as of August 20, 2003, between IPL and The Bank of New York Mellon Trust Company, N.A., as successor trustee (the "Indenture"), pursuant to an Officer's Certificate provided pursuant to the Indenture setting forth the terms of the Debentures, dated as of September 11, 2025 (the "Certificate"). The Offering is expected to close, subject to standard closing conditions, on September 11, 2025. The Debentures are registered under the Securities Act of 1933, as amended, pursuant to an automatic shelf registration statement on Form S-3 (Registration No. 333-276062-01) that IPL filed with the Securities and Exchange Commission (the "SEC") on December 15, 2023 (the "Registration Statement"). The Registration Statement was supplemented by a Prospectus Supplement setting forth the terms of the Debentures that IPL filed with the SEC on September 10, 2025. This Current Report on Form 8-K is being filed for the purpose of filing exhibits to the Registration Statement relating to the public offering of the Debentures, and all such exhibits are hereby incorporated into the Registration Statement by reference. The Underwriting Agreement is filed as Exhibit 1.1 and the Certificate is filed as Exhibit 4.1 to this Form 8-K. On September 8, 2025, IPL issu

01 Financial Statements and Exhibits

Item 9.01 Financial Statements and Exhibits. (d) Exhibits Exhibit No. Description 1.1 Underwriting Agreement, dated September 8, 2025, among Interstate Power and Light Company and the underwriters named therein. 4.1 Officer's Certificate, dated September 11, 2025, creating the 5.600% Senior Debentures due 2055 of Interstate Power and Light Company. 5.1 Opinion of Perkins Coie LLP, dated September 11, 2025, with respect to the 5.600% Senior Debentures due 2055 of Interstate Power and Light Company. 5.2 Opinion of Simmons Perrine Moyer Bergman PLC, dated September 11, 2025, with respect to the 5.600% Senior Debentures due 2055 of Interstate Power and Light Company. 23.1 Consent of Perkins Coie LLP (contained in Exhibit 5.1 hereto). 23.2 Consent of Simmons Perrine Moyer Bergman PLC (contained in Exhibit 5.2 hereto). 99.1 Press Release of Interstate Power and Light Company, dated September 8, 2025. 104 Cover Page Interactive Data File (embedded within the Inline XBRL document).

SIGNATURES

SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, Alliant Energy Corporation and Interstate Power and Light Company have each duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. ALLIANT ENERGY CORPORATION Date: September 11, 2025 By: /s/ Robert J. Durian Robert J. Durian Executive Vice President and Chief Financial Officer INTERSTATE POWER AND LIGHT COMPANY Date: September 11, 2025 By: /s/ Robert J. Durian Robert J. Durian Executive Vice President and Chief Financial Officer

View Full Filing

View this 8-K filing on SEC EDGAR