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): April 6, 2018 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)) 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 ☐ ITEM 8.01 Other Events. On April 6, 2018, Union Electric Company, doing business as Ameren Missouri (“Ameren Missouri”), a subsidiary of Ameren Corporation, issued and sold $425 million principal amount of its 4.000% First Mortgage Bonds due 2048 (the “Bonds”). The Bonds were issued pursuant to a Registration Statement on Form S-3 (File No. 333-222108-02), which became effective on December 15, 2017, and a Prospectus Supplement dated April 3, 2018, to a Prospectus dated December 15, 2017. Ameren Missouri received net offering proceeds of approximately $419.4 million, before expenses, upon closing of the transaction. Ameren Missouri intends to use the net offering proceeds to repay short-term debt, including short-term debt that Ameren Missouri incurred in connection with the repayment at maturity of $178.5 million aggregate principal amount of its 6.00% senior secured notes due April 1, 2018. 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 1.1 Underwriting Agreement, dated April 3, 2018, between Ameren Missouri and the several underwriters named therein, for whom Barclays Capital Inc., MUFG Securities Americas Inc., RBC Capital Markets, LLC, and TD Securities (USA) 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 as of April 1, 2018, by and between Ameren Missouri and The Bank of New York Mellon, as successor trustee, relating to the 4.000% First Mortgage Bonds due 2048. 5.1 Opinion of Gregory L. Nelson, Esq., Senior Vice President, General Counsel and Secretary 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). * 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 thereunto 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/ Martin J. Lyons, Jr. Name: Martin J. Lyons, Jr. Title: Executive Vice President and Chief Financial Officer UNION ELECTRIC COMPANY (Registrant) By: /s/ Michael L. Moehn Name: Michael L. Moehn Title: Chairman and President Date: April 6, 2018