X0609 4 2026-09-08 0 0002070849 BillionToOne, Inc. BLLN 0002088549 Atay Oguzhan false C/O BILLIONTOONE, INC. 1035 O'BRIEN DRIVE MENLO PARK CA 94025 1 1 0 0 Chairman and CEO 0 Class A Common Stock 2026-09-08 4 C 0 20000 0 A 20000 D Class A Common Stock 2026-09-09 4 G 0 20000 0 D 0 D Class B Common Stock 2026-09-08 4 C 0 20000 0 D Class A Common Stock 20000 2197542 D These shares of Class B common stock were converted at a 1:1 ratio for shares of Class A common stock at the option of the holder. Each share of Class B Common Stock is convertible into one share of Class A common stock at the option of the holder. Class B common stock will convert automatically on a one-for-one basis into shares of the Issuer's Class A common stock upon the earliest of (i) seven years from the date of filing of the amended and restated certificate of incorporation, in connection with the Offering and (ii) the date specified by a vote of the holders of Class B common stock representing a majority of the outstanding shares of Class B common stock. /s/ Thomas P. Lynch, Attorney-in-Fact 2026-09-10