SEC Form 4 · accession 0002070849-26-000067

BillionToOne, Inc. · BLLN

Statement of changes in beneficial ownership, as filed. Original on EDGAR ↗

Reporting owner

Thomas P. Lynch

Officer — See Remarks

Period of report

Sep 8, 2026

Accepted (ET)

Sep 10, 2026 · 7:44 pm EDT

Rule 10b5-1 plan

yes — trade under a plan

Issuer CIK

0002070849

Table I — non-derivative securities

Security	Date	Code	Shares	Price	A/D	Owned after	D/I
Class A Common Stock	Sep 8, 2026	M	11,042	$8.65	A	11,742	D
Class A Common Stock	Sep 8, 2026	M	3,969	$11.55	A	15,711	D
Class A Common Stock	Sep 8, 2026	M	1,663	$17.12	A	17,374	D
Class A Common Stock	Sep 8, 2026	M	3,326	$30.78	A	20,700	D
Class A Common Stock	Sep 8, 2026	S	38	$96.4739	D	20,662	D
Class A Common Stock^F2	Sep 8, 2026	S	1,944	$98.9662	D	18,718	D
Class A Common Stock^F3	Sep 8, 2026	S	8,285	$100.1228	D	10,433	D
Class A Common Stock^F4	Sep 8, 2026	S	775	$100.8289	D	9,658	D
Class A Common Stock^F5	Sep 8, 2026	S	614	$98.9986	D	9,044	D
Class A Common Stock^F3	Sep 8, 2026	S	2,997	$100.1135	D	6,047	D
Class A Common Stock^F6	Sep 8, 2026	S	358	$100.8234	D	5,689	D
Class A Common Stock^F7	Sep 8, 2026	S	385	$99.223	D	5,304	D
Class A Common Stock^F8	Sep 8, 2026	S	1,131	$100.3261	D	4,173	D
Class A Common Stock^F9	Sep 8, 2026	S	147	$101.4077	D	4,026	D
Class A Common Stock^F2	Sep 8, 2026	S	576	$98.8882	D	3,450	D
Class A Common Stock^F10	Sep 8, 2026	S	2,518	$100.1959	D	932	D
Class A Common Stock^F11	Sep 8, 2026	S	232	$100.9242	D	700	D

Table II — derivative securities

Security	Conv. / exercise price	Date	Code	Shares	A/D	Exercisable	Expires	Underlying	Underlying shares	Owned after	D/I
Stock Option (right to buy)^F12	$8.65	Sep 8, 2026	M	11,042	D	—	Jan 18, 2033	Class A Common Stock	11,042	68,358	D
Stock Option (right to buy)^F12	$11.55	Sep 8, 2026	M	3,969	D	—	Oct 17, 2033	Class A Common Stock	3,969	11,031	D
Stock Option (right to buy)^F12	$17.12	Sep 8, 2026	M	1,663	D	—	Oct 16, 2034	Class A Common Stock	1,663	8,337	D
Stock Option (right to buy)^F12	$30.78	Sep 8, 2026	M	3,326	D	—	Sep 30, 2035	Class A Common Stock	3,326	36,674	D

Explanation of responses

F1The transactions reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on June 8, 2026.
F10The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $99.670 to $100.550 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
F11The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $100.725 to $101.650 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
F12The options are fully vested and exercisable. The terms of the underlying option grant are as previously reported on the Reporting Person's Form 3 filed on November 5, 2025.
F2The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $98.340 to $99.230 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
F3The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $99.585 to $100.565 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
F4The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $100.620 to $100.9125 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
F5The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $98.340 to $99.195 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
F6The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $100.720 to $100.9025 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
F7The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $98.830 to $99.825 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
F8The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $99.830 to $100.790 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
F9The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $100.890 to $101.870 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

Remarks

General Counsel, Chief Compliance Officer and Secretary