PUBLIC NOTICE Notice of Proposed Tariff Changes Electric Service Schedule Ill. C. C. No. 1 To the Electric Patrons of Ameren Illinois Company d/b/a Ameren Illinois: Ameren Illinois (or Company) hereby gives notice to the public that on April 1, 2026, it filed with the Illinois Commerce Commission (ICC or Commission) evidence (direct testimony) regarding the reconciliation of revenues collected from its electric customers under the Company's Hazardous Materials Adjustment Clause (HMAC) Rider, with actual and prudent associated costs from January 1, 2025 through December 31, 2025. The HMAC Rider is applicable to Rate Zone III only (formerly Illinois Power Company d/b/a AmerenIP service territory). This reconciliation may result in changes to the Company's rates and charges with respect to electric delivery services in the Company's Rate Zone III service area in Illinois. The changes in rates and charges will take effect after hearings and after the Commission issues its final Order. The Commission docketed the filing as Docket No. 26-0963. A copy of the evidence may be inspected at Ameren Illinois' offices located at 300 Liberty Street, Peoria, Illinois or online at www.icc.illinois.gov/e-docket/. All parties interested in this matter may obtain information with respect thereto either directly from Ameren Illinois or by addressing the Chief Clerk of the Illinois Commerce Commission, 527 East Capitol Avenue, Springfield, Illinois 62706. AMEREN ILLINOIS COMPANY d/b/a Ameren Illinois By: Patrick Smith, President IPL0362016 Aug 2,9 2026