SOUTHERN CO (SO) · Insider Trading (Form 4) SEC Filing

=== SEC Form 4 — Statement of Changes in Beneficial Ownership === Document Type: 4 Period of Report: 2026-06-28 10b5-1 Pre-arranged Plan: No --- Issuer --- Name: SOUTHERN CO (SO) CIK: 0000092122 --- Reporting Owner --- Name: Sena Peter P III CIK: 0002023851 Role: Officer (Chairman,President & CEO, SNC) --- Non-Derivative Transactions --- [Transaction #1] Security: Southern Company Common Stock Date: 2026-06-28 | Code: M (Exercise of derivative) Shares: +712 | Price: $0.00 Shares Owned After: 31,517 | Ownership: D (Direct) Footnotes: [F1] Shares acquired upon vesting of second 1/3 of performance restricted stock units granted on June 28, 2024. Includes 45 accrued dividend equivalent units. [Transaction #2] Security: Southern Company Common Stock Date: 2026-06-28 | Code: F (Payment of exercise/tax) Shares: -316 | Price: $97.16 Total Value: $30,702.56 Shares Owned After: 31,201 | Ownership: D (Direct) Footnotes: [F2] Shares withheld to satisfy required state and federal tax withholding requirements. --- Derivative Transactions --- [Transaction #1] Security: Performance Restricted Stock Units Date: 2026-06-28 | Code: M (Exercise of derivative) Shares: -667 | Price: $0.00 Shares Owned After: 667 | Ownership: D (Direct) Footnotes: [F3] Represents second 1/3 of performance restricted stock units granted on June 28, 2024. The remaining award will vest in 2027. Each restricted stock unit represents the right to receive, at settlement, one share of common stock. Additional units will be acquired with deemed dividends. Shares will be withheld upon vesting to satisfy tax requirements. [F3] Represents second 1/3 of performance restricted stock units granted on June 28, 2024. The remaining award will vest in 2027. Each restricted stock unit represents the right to receive, at settlement, one share of common stock. Additional units will be acquired with deemed dividends. Shares will be withheld upon vesting to satisfy tax requirements. [F3] Represents second 1/3 of performance restricted stock units granted on June 28, 2024. The remaining award will vest in 2027. Each restricted stock unit represents the right to receive, at settlement, one share of common stock. Additional units will be acquired with deemed dividends. Shares will be withheld upon vesting to satisfy tax requirements. [F3] Represents second 1/3 of performance restricted stock units granted on June 28, 2024. The remaining award will vest in 2027. Each restricted stock unit represents the right to receive, at settlement, one share of common stock. Additional units will be acquired with deemed dividends. Shares will be withheld upon vesting to satisfy tax requirements. --- Footnotes (Complete Index) --- F1: Shares acquired upon vesting of second 1/3 of performance restricted stock units granted on June 28, 2024. Includes 45 accrued dividend equivalent units. F2: Shares withheld to satisfy required state and federal tax withholding requirements. F3: Represents second 1/3 of performance restricted stock units granted on June 28, 2024. The remaining award will vest in 2027. Each restricted stock unit represents the right to receive, at settlement, one share of common stock. Additional units will be acquired with deemed dividends. Shares will be withheld upon vesting to satisfy tax requirements. --- Signature --- /s/ /s/ Brittney Anderson, Attorney-in-Fact for Peter P. Sena, III (2026-06-29)