STOCK TITAN

BillionToOne CTO converts, gifts 20K shares

BillionToOne CTO David Tsao converted 20,000 Class B shares to Class A, then gifted 20,000 Class A shares, while retaining over 2.3 million Class B shares.

(Neutral)
(Neutral)
Form Type
4

Rhea-AI Filing Summary

BillionToOne, Inc. (BLLN) director and Chief Technology Officer David Tsao reported a series of internal equity moves. On September 3, 2026, he converted 20,000 shares of Class B common stock into 20,000 shares of Class A common stock at a 1:1 ratio, leaving 2,305,108 Class B shares held directly. On September 8, 2026, he made a bona fide gift of 20,000 Class A shares at a reported price of $0.00 per share. Class B shares are convertible into Class A on a one-for-one basis at the holder’s option and will automatically convert on specified future events. No Rule 10b5-1 trading plan is reported for these transactions.

Positive

  • None.

Negative

  • None.
Insider Tsao David
Role Chief Technology Officer
Type Security Shares Price Value
Gift Class A Common Stock 20,000 $0.00 $0.00
Conversion Class B Common Stock F1, F2 20,000 $0.00 $0.00
Conversion Class A Common Stock F1 20,000 $0.00 $0.00
Holdings After Transaction: Class B Common Stock — 2,305,108 contracts (Direct); Class A Common Stock — 1,000 shares (Direct)
Footnotes (2)
  1. F1. 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.
  2. F2. 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.
Class A shares gifted 20,000 shares Bona fide gift of Class A common stock on September 8, 2026
Class B shares converted 20,000 shares Conversion of Class B into Class A on September 3, 2026
Class B holdings after conversion 2,305,108 shares Direct Class B common stock held after September 3, 2026 transaction
Conversion ratio 1 Class B share for 1 Class A share Each Class B share convertible into one Class A share at holder’s option
Reported gift price $0.00 per share Bona fide gift of 20,000 Class A shares on September 8, 2026
Automatic conversion timing trigger 7 years Automatic Class B to Class A conversion seven years from amended and restated charter filing
bona fide gift financial
"The September 8, 2026 transaction is described as a bona fide gift"
A bona fide gift is a genuine, voluntary transfer of money, property, or benefits from one party to another made without expectation of repayment, services, or hidden conditions. Investors care because such gifts can affect company disclosures, related‑party transaction rules, tax treatment, and perceived conflicts of interest; think of it like someone giving you a present with no strings attached — but on a corporate scale, auditors and regulators need to verify it really is unconditional.
Conversion of derivative security financial
"The September 3, 2026 entries are coded as Conversion of derivative security"
Class B common stock financial
"Each share of Class B common stock is convertible into one share of Class A"
A class B common stock is one of multiple types of a company’s ordinary shares that carries specific rights—often different voting power or dividend priority—compared with other classes. For investors it matters because those differences affect how much influence you have over company decisions, the income you might receive, and how freely the shares trade; think of it like owning a car with different keys: some keys let you start the engine and open the trunk, others only unlock the door.
amended and restated certificate of incorporation regulatory
"Automatic conversion is tied to the amended and restated certificate of incorporation"
A company’s amended and restated certificate of incorporation is an updated version of its foundational legal charter that replaces the older document and folds in all changes into one clear copy; it spells out corporate structure, classes of stock, shareholder rights and key governance rules. Investors care because it can change who controls the company, how votes are counted, what claims shareholders have on assets or dividends, and can introduce or remove protections against takeovers—like updating a house title after a major renovation to show who owns what and under what rules.

FAQ

What insider transactions did BLLN’s CTO David Tsao report on this Form 4?

He reported converting 20,000 Class B shares into 20,000 Class A shares on September 3, 2026, and then making a bona fide gift of 20,000 Class A shares on September 8, 2026.

How many BillionToOne (BLLN) Class B shares does David Tsao hold after these transactions?

After the September 3, 2026 conversion, David Tsao directly held 2,305,108 shares of BillionToOne’s Class B common stock, as reported in the filing.

What was the conversion ratio between BLLN Class B and Class A shares in David Tsao’s Form 4?

The filing states that each share of Class B common stock is convertible into one share of Class A common stock, a 1:1 conversion ratio exercised for 20,000 shares.

Did BillionToOne’s CTO sell any shares for cash in this Form 4?

No. The reported transactions are a conversion of 20,000 Class B shares into Class A and a bona fide gift of 20,000 Class A shares. The gift shows a price of $0.00 per share, indicating no sale proceeds.

Were BLLN insider transactions made under a Rule 10b5-1 trading plan?

The document-level Rule 10b5-1 checkbox is not checked, and there is no footnote indicating a plan, so no Rule 10b5-1 trading plan is reported for these transactions.

What automatic conversion features apply to BillionToOne (BLLN) Class B common stock?

Class B common stock will convert into Class A on a one-for-one basis upon the earliest of seven years from filing of the amended and restated certificate of incorporation in connection with the offering, or a majority vote of Class B holders.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Learn about SEC filing dates
SEC Form 4
FORM 4UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940
OMB APPROVAL
OMB Number:3235-0287
Estimated average burden
hours per response:0.5
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.
1. Name and Address of Reporting Person*
Tsao David

(Last)(First)(Middle)
C/O BILLIONTOONE, INC.
1035 O'BRIEN DRIVE

(Street)
MENLO PARK CALIFORNIA 94025

(City)(State)(Zip)

UNITED STATES

(Country)
2. Issuer Name and Ticker or Trading Symbol
BillionToOne, Inc. [ BLLN ]
5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
XDirector10% Owner
XOfficer (give title below)Other (specify below)
Chief Technology Officer
2a. Foreign Trading Symbol
3. Date of Earliest Transaction (Month/Day/Year)
09/03/2026
6. Individual or Joint/Group Filing (Check Applicable Line)
XForm filed by One Reporting Person
Form filed by More than One Reporting Person
4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year)2A. Deemed Execution Date, if any (Month/Day/Year)3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4)
CodeVAmount(A) or (D)Price
Class A Common Stock09/03/2026C(1)20,000A$0(1)21,000D
Class A Common Stock09/08/2026G20,000D$01,000D
Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year)3A. Deemed Execution Date, if any (Month/Day/Year)4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 6. Date Exercisable and Expiration Date (Month/Day/Year)7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4)
CodeV(A)(D)Date ExercisableExpiration DateTitleAmount or Number of Shares
Class B Common Stock(1)(2)09/03/2026C20,000 (2) (2)Class A Common Stock20,000$0(1)2,305,108D
Explanation of Responses:
1. 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.
2. 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.
Remarks:
/s/ Thomas P. Lynch, Attorney-in-Fact09/08/2026
** Signature of Reporting PersonDate
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)

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