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) September 5, 2023 Commission File Number Registrant, State of Incorporation, Address and Telephone Number I.R.S. Employer Identification No. 1-3526 The Southern Company 58-0690070 (A Delaware Corporation) 30 Ivan Allen Jr. Boulevard, N.W . Atlanta , Georgia 30308 ( 404 ) 506-5000 The name and address of the registrant have not changed since the last report. Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant 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)) Securities registered pursuant to Section 12(b) of the Act: Registrant Title of each class Trading Symbol(s) Name of each exchange on which registered The Southern Company Common Stock, par value $5 per share SO New York Stock Exchange The Southern Company Series 2017B 5.25% Junior Subordinated Notes due 2077 SOJC New York Stock Exchange The Southern Company Series 2020A 4.95% Junior Subordinated Notes due 2080 SOJD New York Stock Exchange The Southern Company Series 2020C 4.20% Junior Subordinated Notes due 2060 SOJE New York Stock Exchange The Southern Company Series 2021B 1.875% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2081 SO 81 New York Stock Exchange 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   ☐ 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.   ☐ Item 8.01. Other Events . On September 5, 2023, The Southern Company (the “Company”) entered into Underwriting Agreements covering the issue and sale of $600,000,000 aggregate principal amount of its Series 2023D 5.50% Senior Notes due March 15, 2029 (the “Series 2023D Senior Notes”) and $700,000,000 aggregate principal amount of its Series 2023E 5.70% Senior Notes due March 15, 2034 (the “Series 2023E Senior Notes”). Both the Series 2023D Senior Notes and the Series 2023E Senior Notes were registered under the Securities Act of 1933, as amended, pursuant to the shelf registration statement (Registration No. 333-253286) of the Company. Item 9.01. Financial Statements and Exhibits. (d) Exhibits. 1.3(a) Underwriting Agreement relating to the Series 2023 D Senior Notes, dated September 5, 2023, among the Company and Barclays Capital Inc., MUFG Securities Americas Inc., RBC Capital Markets, LLC, Scotia Capital (USA) Inc. and Wells Fargo Securities, LLC , as representatives of the several Underwriters named in Schedule I thereto. 1.3(b) Underwriting Agreement relating to the Series 2023 E Senior Notes, dated September 5, 2023, among the Company and Barclays Capital Inc., MUFG Securities Americas Inc., PNC Capital Markets LLC, Scotia Capital (USA) Inc . and Wells Fargo Securities, LLC, as representatives of the several Underwriters named in Schedule I thereto. 4.4(a) Thirtieth Supplemental Indenture to Senior Note Indenture dated as of September 8, 2023, providing for the issuance of the Series 2023D Senior Notes . 4.4(b) Thirty-First Supplemental Indenture to Senior Note Indenture dated as of September 8, 2023, providing for the issuance of the Series 2023E Senior Notes. 4.9(a) Form of the Series 2023D Senior Note (included in Exhibit 4.4(a) above). 4.9(b) Form of the Series 2023E Senior Note (included in Exhibit 4.4(b) above). 5.1(a) Opinion of Troutman Pepper Hamilton Sanders LLP relating to the Series 2023D Senior Notes . 5.1(b) Opinion of Troutman Pepper Hamilton Sanders LLP relating to the Series 2023E Senior Notes . 8.1(a) Tax Opinion of Troutman Pepper Hamilton Sanders LLP relating to the Series 2023D Senior Notes. 8.1(b) Tax Opinion of Troutman Pepper Hamilton Sanders LLP relating to the Series 2023E Senior Notes. 23.1 Consent of Troutman Pepper Hamilton Sanders LLP (included in Exhibit 5.1(a) above). 23.2 Consent of Troutman Pepper Hamilton Sanders LLP (included in Exhibit 5.1(b) above). 23.3 Consent of Troutman Pepper Hamilton Sanders LLP (included in Exhibit 8.1(a) above). 23.4 Consent of Troutman Pepper Hamilton Sanders LLP (included in Exhibit 8.1(b) above). 104 Cover Page Interactive Data File – The cover page iXBRL tags are embedded within the inline XBRL document. 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:   September 8, 2023 THE SOUTHERN COMPANY By /s/Melissa K. Caen Melissa K. Caen Assistant Secretary 2