8-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) ofthe Securities Exchange Act of 1934

Date of report (Date of earliest event reported):February 26, 2025

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:

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).

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.

Reference is made to Note 2 – Rate and Regulatory Matters to the financial statements under Part II, Item 8. Financial Statements and to Overview and Outlook under Part II, Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations, each in the Annual Report on Form 10-K for the year ended December 31, 2024 (“Form 10-K”), of registrants Ameren Corporation and Union Electric Company, doing business as Ameren Missouri (“Ameren Missouri”), for a discussion of Ameren Missouri’s electric service regulatory rate review filed with the Missouri Public Service Commission (“MoPSC”) in June 2024.

On February 26, 2025, Ameren Missouri, the staff of the MoPSC, the Missouri Office of Public Counsel, and certain other intervenors reached an agreement in principle (the "Agreement") that would resolve all revenue requirement issues in connection with Ameren Missouri's June 2024 electric service regulatory rate review. Ameren Missouri expects to work with the other parties to the Agreement to finalize a stipulation and agreement reflecting the terms of the Agreement. Any stipulation and agreement will be subject to approval by the MoPSC. Ameren Missouri cannot predict whether the MoPSC will approve any stipulation and agreement or, if approved, whether any application for rehearing or appeal will be filed or the outcome if so filed.

A MoPSC decision in connection with the rate review is expected by May 2025, with new rates effective by June 2025.

This combined Form 8-K is being filed separately by Ameren Corporation and Union Electric Company. 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.

1

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.

Date: March 3, 2025

2