David Tsao - 10 Aug 2026 Form 4 Insider Report for BillionToOne, Inc. (BLLN)

Reporting relationship: Chief Technology Officer, Director
Issuer ticker: BLLN
Reported as of: 10 Aug 2026
Net transaction value: -$928,600
SEC form: 4
Accepted by SEC: 12 Aug 2026, 18:51:52 UTC
Prior SEC filing: 15 Jul 2026
Source filing: View source filing
Reporting owner signature: /s/ Thomas P. Lynch, Attorney-in-Fact

Key filing fact

David Tsao filed Form 4 for BillionToOne, Inc. (BLLN) on 12 Aug 2026.

Key facts

This page summarizes David Tsao's Form 4 filing for BillionToOne, Inc. (BLLN).
3 reported transactions and 1 derivative row are listed below.
Accepted by SEC: 12 Aug 2026, 18:51.

Change

Previous filing in this sequence was filed on 15 Jul 2026.
Current net transaction value: -$928,600.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (1)

CIK 0002087127 Primary reporting owner

Tsao David

Relationship: Chief Technology Officer, Director
Address: C/O BILLIONTOONE, INC., 1035 O'BRIEN DRIVE, MENLO PARK
Signature: /s/ Thomas P. Lynch, Attorney-in-Fact
Signature date: 12 Aug 2026

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

BLLN transaction

Class A Common Stock

Options Exercise

Transaction value
Shares: +10,000
Change %: +1000%
Price: $2.80^*
Shares after: 11,000
Date: 10 Aug 2026
Ownership: Direct
Footnotes: F1

BLLN transaction

Class A Common Stock

Sale

Transaction value: $928,600
Shares: -10,000
Change %: -91%
Price: $92.86
Shares after: 1,000
Date: 10 Aug 2026
Ownership: Direct
Footnotes: F1

Reported derivative securities

Options, warrants, convertible securities, or similar derivative positions disclosed in the filing.

BLLN transaction Derivative

Stock Option (right to buy)

Options Exercise

Transaction value
Shares: -10,000
Change %: -1.7%
Price: $2.80^*
Shares after: 590,000
Date: 10 Aug 2026
Ownership: Direct
Underlying class: Class A Common Stock
Underlying amount: 10,000
Exercise price: $2.80
Footnotes: F2

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Rule 10b5-1 trading plan

These transactions were reported as open-market trades under a Rule 10b5-1 plan. The plan lets an insider set trading instructions in advance, which can reduce the risk of trading while in possession of material nonpublic information.

Original filing language: transaction made pursuant to a contract, instruction, or written plan intended to satisfy Rule 10b5-1(c).

Explanation of responses 2 footnotes

Footnote F1

The transactions reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on March 6, 2026.

Footnote F2

The options are fully vested and exercisable.