AMEREN CORP

Insider Adoption or Termination of Trading Arrangements

During the fiscal quarter ended September 30, 2026, none of our directors or officers informed us of theadoption ortermination of a “Rule 10b5-1 trading arrangement” or “non-Rule 10b5-1 trading arrangement,” as those terms are defined in Regulation S-K, Item 408, except as follows:

On August 6, 2026, Theresa A. Shaw, Senior Vice President, Chief Accounting and Transformation Officer of Ameren, adopted a Rule 10b5-1 trading arrangement that provides for the sale of up to an aggregate of approximately 7,640 shares, consisting of:

•up to 500 shares on a quarterly basis between November 2026 and November 2027, subject to certain price limitations set forth in the trading arrangement; and

•shares acquired upon vesting of certain equity awards, consisting of (i) 100% of shares delivered from the 2024 restricted stock units award scheduled to vest on March 1, 2027 (approximately 1,692 shares before applicable tax withholding), and (ii) 5% of shares delivered from the 2024 performance condition performance share units and 2024 market condition performance share units awards scheduled to vest on March 1, 2027 (approximately 564 shares and 3,384 shares, respectively, before applicable performance adjustments and tax withholding).

Ms. Shaw’s 10b5-1 trading arrangement will terminate on the earlier of: (i)November 16, 2027; (ii) execution of all trades or expiration of all orders relating to such trades under the Rule 10b5-1 trading arrangement; or (iii) such date as the Rule 10b5-1 trading arrangement is otherwise terminated according to its terms.

The trading arrangement discussed above is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).