SO: Other company developments

Item 8.01. Other Events. Advance Notice Deadline for 2027 Annual Meeting of Stockholders The Company held its 2026 Annual Meeting of Stockholders on May 13, 2026. As a result of the Amended and Restated By-Laws discussed in Item 5.03 above, the advance notice provisions’ deadline 3 for submission of written notice of director nominations or other business by stockholders (other than a proposal submitted for inclusion in the Company’s proxy materials under Exchange Act Rule 14a-8) for the Company’s 2027 Annual Meeting of Stockholders is no earlier than January 13, 2027 and no later than February 12, 2027. Item 9.01. Financial Statements and Exhibits. (d) Exhibits. 3.1 Amended and Restated By-Laws of Southern Company, effective October 20, 2026 . 104 Cover Page Interactive Data File – The cover page iXBRL tags are embedded within the inline XBRL document. 4 SIGNATURE Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: October 22, 2026 THE SOUTHERN COMPANY By /s/Melissa K. Caen Melissa K. Caen Assistant Secretary 5