Company Update

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549       FORM  8-K       CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934   Date of report (Date of earliest event reported): February 27, 2026         Commission File Number   Exact Name of Registrant as Specified in Charter; State of Incorporation; Address and Telephone Number   IRS Employer Identification Number   1-14756     Ameren Corporation ( Missouri Corporation) 1901 Chouteau Avenue St. Louis , Missouri 63103 ( 314 ) 621-3222       43-1723446 1-2967   Union Electric Company ( Missouri Corporation) 1901 Chouteau Avenue St. Louis , Missouri 63103 ( 314 ) 621-3222   43-0559760   Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrants under any of the following provisions: ¨ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ¨ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) ¨ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ¨ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))   Securities registered pursuant to Section 12(b) of the Act:   Title of each class   Trading Symbol(s)   Name of each exchange on which registered Common Stock, $0.01 par value per share   AEE   New York Stock Exchange   Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).     Emerging growth company   Ameren Corporation ¨   Union Electric Company ¨     If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.   Ameren Corporation ¨   Union Electric Company ¨       Co-Registrant CIK 0000100826 Co-Registrant Amendment Flag false Co-Registrant Form Type 8-K Co-Registrant DocumentperiodEndDate 2026-02-27 Co-Registrant Written Commuunications false Co-Registrant Solicitating Materials false Co-Registrant PreCommencement Tender Offer false Co-Registrant PreCommencement Tender Offer false Co-Registrant Entity PreCommencement Issuer Tender Offer false         ITEM 8.01 Other Events.   On February 27, 2026, Union Electric Company, doing business as Ameren Missouri (“Ameren Missouri”), a subsidiary of Ameren Corporation, sold $450 million principal amount of its 4.80% First Mortgage Bonds due 2036 (the “2036 Bonds”) and $450 million principal amount of its 5.55% First Mortgage Bonds due 2056 (the “2056 Bonds”, and together with the 2036 Bonds, the “Bonds”). The Bonds were offered pursuant to a Registration Statement on Form S-3 (File No. 333-274977-02), which became effective on October 13, 2023, and a Prospectus Supplement dated February 23, 2026, to a Prospectus dated October 13, 2023. Ameren Missouri received aggregate net offering proceeds of approximately $891.1 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   Underwriting Agreement relating to the Bonds, dated February 23, 2026, between Ameren Missouri and the several underwriters named therein, for whom Barclays Capital Inc., BofA Securities, Inc., Mizuho Securities USA LLC, MUFG Securities Americas Inc., and Wells Fargo Securities, LLC are acting as representatives.       4.1*   Indenture of Mortgage and Deed of Trust, dated June 15, 1937, from Ameren Missouri to The Bank of New York Mellon, as successor trustee, as amended May 1, 1941, and Second Supplemental Indenture dated May 1, 1941 (Exhibit B-1, File No. 2-4940).       4.2   Supplemental Indenture, dated February 1, 2026, by and between Ameren Missouri and The Bank of New York Mellon, as successor trustee, relating to the 4.80% First Mortgage Bonds due 2036 and the 5.55% First Mortgage Bonds due 2056.       5.1   Opinion of Stephen C. Lee, Esq., Vice President and Deputy General Counsel of Ameren Missouri, 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 Data File (formatted as Inline XBRL).     * Incorporated by reference as indicated.   This combined Form 8-K is being filed separately by Ameren Corporation and Union Electric Company (each a “registrant”). Information contained herein relating to any individual registrant has been filed by such registrant on its own behalf. No registrant makes any representation as to information relating to any other registrant.   - 2 -     SIGNATURES   Pursuant to the requirements of the Securities Exchange Act of 1934, each registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. The signature for each undersigned company shall be deemed to relate only to matters having reference to such company or its subsidiaries.     AMEREN CORPORATION   (Registrant)       By: /s/ Leonard P. Singh   Name: Leonard P. Singh   Title: Executive Vice President and Chief Financial Officer       UNION ELECTRIC COMPANY   (Registrant)       By: /s/ Michael L. Moehn   Name: Michael L. Moehn   Title: Interim Chairman and President   Date: February 27, 2026   - 3 -