AEE: Other company developments

ITEM 8.01 Other Events. On August 24, 2026, Ameren Illinois Company (“Ameren Illinois”), a subsidiary of Ameren Corporation, sold $400 million principal amount of its 5.50% First Mortgage Bonds due 2036 (the “Bonds”). The Bonds were offered pursuant to a Registration Statement on Form S-3 (File No. 333-297949-01), which became effective on August 4, 2026, and a Prospectus Supplement dated August 17, 2026, to a Prospectus dated August 4, 2026. Ameren Illinois received net offering proceeds of approximately $397.4 million, before expenses, upon closing of the transaction. This Current Report on Form 8-K is being filed to report as exhibits certain documents in connection with the offering of the Bonds. ITEM 9.01 Financial Statements and Exhibits. (d) Exhibits Exhibit Number Title 1.1 Underwriting Agreement relating to the Bonds, dated August 17, 2026, between Ameren Illinois and the several underwriters named therein, for whom Goldman Sachs & Co. LLC, KeyBanc Capital Markets Inc., SMBC Nikko Securities America, Inc. and TD Securities (USA) LLC are acting as representatives. 4.1* General Mortgage Indenture and Deed of Trust, dated as of November 1, 1992, from Ameren Illinois to The Bank of New York Mellon Trust Company, N.A., as successor trustee (1992 Form 10-K, Exhibit 4(cc), File No. 1-3004). 4.2 Supplemental Indenture, dated as of August 1, 2026, by and between Ameren Illinois and The Bank of New York Mellon Trust Company, N.A., as successor trustee, relating to the Bonds. 5.1 Opinion of David M. Feinberg, Esq., Executive Vice President, General Counsel and Secretary of Ameren Illinois, regarding the legality of the Bonds (including consent). 5.2 Opinion of Morgan, Lewis & Bockius LLP regarding the legality of the Bonds (including consent). 104 Cover Page Interactive D