X0609 4 2026-06-30 0001541119 Sound Financial Bancorp, Inc. SFBC 0001410558 Stewart Laura Lee false C/O SOUND FINANCIAL BANCORP, INC. 2400 3RD AVENUE, SUITE 150 SEATTLE WA 98121 1 1 President and CEO 1 Common Stock 14409 I By ESOP Common Stock 18906 I By 401(k) Common Stock 2026-06-30 4 S 0 900 42.60 D 9000 I By CRT Common Stock 49602 D Stock Option (Right to Buy) 33.5000 2029-01-25 Common Stock 250 250 D Stock Option (Right to Buy) 36.2600 2030-01-31 Common Stock 120 120 D Stock Option (Right to Buy) 32.4600 2031-01-27 Common Stock 300 300 D Stock Option (Right to Buy) 40.1300 2033-01-27 Common Stock 1800 1800 D Stock Option (Right to Buy) 39.8900 2034-01-26 Common Stock 259 259 D Options are fully exercisable. Options vest in three equal annual installments beginning on January 26, 2025. On December 10, 2025, the reporting person contributed 10,800 shares of Sound Financial Bancorp, Inc. common stock to the Stewart Charitable Remainder Trust ("CRT") for estate planning purposes, resulting in a change in form of beneficial ownership from direct to indirect. The reporting person is the sole lifetime beneficiary of the CRT and retains the right to receive distributions in accordance with the terms of the trust. An independent third-party trustee serves as the trustee of the CRT and holds sole voting and dispositive power over the shares held by the trust. These shares were sold by the trustee of the CRT, and not at the direction of the reporting person, pursuant to instructions contained in the trust agreement governing the CRT, in accordance with Rule 10b5-1(c) adopted on December 10, 2025. Following the reported transaction, the reporting person continues to hold a meaningful equity interest in the Company through remaining share ownership and outstanding equity awards. /s/ Laura Lee Stewart 2026-06-30