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 March 30, 2026, it filed with the Illinois Commerce Commission evidence (direct testimony) regarding the reconciliation of revenues collected from its electric customers under the Company's Electric Environmental Adjustment (Rider EEA), with costs incurred in connection with certain environmental remediation activities associated with its manufactured gas plant sites in Illinois from January 1, 2025 through December 31, 2025. Rider EEA is applicable to Rate Zones I and III only (formerly the AmerenCIPS and AmerenIP services territories, respectively). This reconciliation may result in changes to the Company's rates and charges with respect to electric delivery services throughout the Company's territories in Illinois. The changes in rates and charges will take effect after hearings and after the Commission issues its final Order. The Commission docketed these filings as Docket Nos. 25-1046 (RZ I) and 25-1048 (RZ III). A copy of the evidence may be inspected at the 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