BillionToOne: David Tsao proposes $2.16M share sale

The notice pairs the proposed sale with a 20,000-share cash option exercise and identifies earlier sales by David Tsao and the DT 2021 Irrevocable Trust.

Rhea-AI Filing Summary

BillionToOne, Inc. (BLLN) lists David Tsao, identified as an officer and director, as proposing to sell 20,000 Class A shares on October 5, 2026, with an aggregate market value of $2,162,950.69. Fidelity Brokerage Services LLC is named as the broker, and NASDAQ as the exchange. The notice also lists a 20,000-share stock option exercise from the issuer for cash on October 5, 2026, and earlier sales by David Tsao and the DT 2021 Irrevocable Trust. The remarks identify Icontrust LLC as trustee and Tsao as an account stakeholder.

Key Figures

Class A shares listed for sale: 20,000 shares Aggregate market value of shares listed for sale: $2,162,950.69 Shares acquired through stock option exercise: 20,000 shares +4 more

7 metrics

Class A shares listed for sale 20,000 shares Approximate sale date October 5, 2026

Aggregate market value of shares listed for sale $2,162,950.69 Proposed sale dated October 5, 2026

Shares acquired through stock option exercise 20,000 shares From the issuer for cash on October 5, 2026

David Tsao prior sale 20,000 shares July 13, 2026

Aggregate value of David Tsao prior sale $2,497,697.77 July 13, 2026

DT 2021 Irrevocable Trust prior sale 3,500 shares July 13, 2026

Aggregate value of DT 2021 Irrevocable Trust prior sale $439,110.00 July 13, 2026

Key Terms

Rule 144, Stock Option Exercise, trustee

3 terms

Rule 144 regulatory

"paragraph (a) of Rule 144"

Rule 144 is a U.S. securities regulation that sets conditions under which restricted or insider-held shares can be legally resold to the public, such as required holding periods, availability of public information, limits on how much can be sold at once, and certain filing requirements. For investors it matters because it determines when previously locked-up shares can enter the market — like a release valve that can increase supply, affect share price, and signal insider intent.

Stock Option Exercise financial

"Stock Option Exercise"

A stock option exercise is the act of using a previously granted right to buy shares of a company's stock at a specific, predetermined price by paying that price and receiving the shares. It matters to investors because exercising changes who owns the shares (which can dilute existing ownership), can trigger taxable events and shift potential gains or losses, and affects voting power and the company’s outstanding share count—like turning a voucher into an actual product that becomes part of circulating supply.

trustee regulatory

"by Icontrust LLC, trustee on the account"

A trustee is a person or institution legally appointed to hold and manage assets or enforce an agreement on behalf of other people (beneficiaries). Think of a trustee as a neutral referee or custodian who must act in the beneficiaries’ best interests, follow the trust or contract rules, and handle distributions, recordkeeping and enforcement. Investors care because a trustworthy trustee protects their rights, ensures promised payments or remedies are delivered, and can influence recoveries if things go wrong.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many BLLN shares does David Tsao plan to sell?

The notice lists 20,000 Class A shares for sale on October 5, 2026, with an aggregate market value of $2,162,950.69. Fidelity Brokerage Services LLC is named as the broker, and NASDAQ as the exchange.

What earlier BLLN sales by the DT 2021 Irrevocable Trust are listed?

The trust's listed sales were 3,500 shares on July 13, 2026, for $439,110.00; 3,500 shares on August 10, 2026, for $325,010.00; and 1,750 shares on September 9, 2026, for $170,695.00. The remarks identify Icontrust LLC as trustee and David Tsao as an account stakeholder.

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

See more from StockTitan in Google Search and AI answers. Adds StockTitan as a preferred source · opens Google

Add on Google Not now

Available on EDGAR 10/05/2026 - 04:11 PM Accepted by SEC EDGAR 10/05/2026 - 04:10 PM Learn about SEC filing dates

Form 144 Filer Information	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 144 NOTICE OF PROPOSED SALE OF SECURITIES PURSUANT TO RULE 144 UNDER THE SECURITIES ACT OF 1933
FORM 144

144: Filer Information

Filer CIK	0002087127
Filer CCC	XXXXXXXX
Is this a LIVE or TEST Filing?	LIVE TEST
Submission Contact Information
Name
Phone
E-Mail Address

144: Issuer Information

Name of Issuer	BillionToOne, Inc.
SEC File Number	001-42934
Address of Issuer	1035 O'BRIEN DRIVE MENLO PARK CALIFORNIA 94025
Phone	650-460-2551
Name of Person for Whose Account the Securities are To Be Sold	Tsao David
See the definition of "person" in paragraph (a) of Rule 144. Information is to be given not only as to the person for whose account the securities are to be sold but also as to all other persons included in that definition. In addition, information shall be given as to sales by all persons whose sales are required by paragraph (e) of Rule 144 to be aggregated with sales for the account of the person filing this notice.
Relationship to Issuer	Officer
Relationship to Issuer	Director

144: Securities Information

Title of the Class of Securities To Be Sold	Name and Address of the Broker	Number of Shares or Other Units To Be Sold	Aggregate Market Value	Number of Shares or Other Units Outstanding	Approximate Date of Sale	Name the Securities Exchange
Class A	Fidelity Brokerage Services LLC 900 Salem Street Smithfield RI 02917	20000	2162950.69	42644388	10/05/2026	NASDAQ

Furnish the following information with respect to the acquisition of the securities to be sold and with respect to the payment of all or any part of the purchase price or other consideration therefor:

144: Securities To Be Sold

Title of the Class	Date you Acquired	Nature of Acquisition Transaction	Name of Person from Whom Acquired	Is this a Gift?	Date Donor Acquired	Amount of Securities Acquired	Date of Payment	Nature of Payment *
Class A	10/05/2026	Stock Option Exercise	Issuer			20000	10/05/2026	Cash

* If the securities were purchased and full payment therefor was not made in cash at the time of purchase, explain in the table or in a note thereto the nature of the consideration given. If the consideration consisted of any note or other obligation, or if payment was made in installments describe the arrangement and state when the note or other obligation was discharged in full or the last installment paid.

Furnish the following information as to all securities of the issuer sold during the past 3 months by the person for whose account the securities are to be sold.

144: Securities Sold During The Past 3 Months

Name and Address of Seller	Title of Securities Sold	Date of Sale	Amount of Securities Sold	Gross Proceeds
David Tsao 1035 O'Brien Drive Menlo Park CA 94025	Class A	07/13/2026	20000	2497697.77
Dt 2021 Irrevocable Trust 1035 O'Brien Drive Menlo Park CA 94025	Class A	07/13/2026	3500	439110.00
David Tsao 1035 O'Brien Drive Menlo Park CA 94025	Class A	08/10/2026	10000	928600.00
Dt 2021 Irrevocable Trust 1035 O'Brien Drive Menlo Park CA 94025	Class A	08/10/2026	3500	325010.00
David Tsao 1035 O'Brien Drive Menlo Park CA 94025	Class A	08/25/2026	10000	1000000.00
David Tsao 1035 O'Brien Drive Menlo Park CA 94025	Class A	09/09/2026	20000	1975400.00
Dt 2021 Irrevocable Trust 1035 O'Brien Drive Menlo Park CA 94025	Class A	09/09/2026	1750	170695.00
David Tsao 1035 O'Brien Drive Menlo Park CA 94025	Class A	09/24/2026	3333	416625.00

144: Remarks and Signature

Remarks	There are sales within the past 3 months which occurred in the account of the Dt 2021 Irrevocable Trust by Icontrust Llc, trustee on the account. David Tsao is an account stakeholder in the Dt 2021 Irrevocable Trust.
Date of Notice	10/05/2026
Date of Plan Adoption or Giving of Instruction, If Relying on Rule 10b5-1	06/05/2026
ATTENTION:
The person for whose account the securities to which this notice relates are to be sold hereby represents by signing this notice that he does not know any material adverse information in regard to the current and prospective operations of the Issuer of the securities to be sold which has not been publicly disclosed. If such person has adopted a written trading plan or given trading instructions to satisfy Rule 10b5-1 under the Exchange Act, by signing the form and indicating the date that the plan was adopted or the instruction given, that person makes such representation as of the plan adoption or instruction date.
Signature	/s/Wade Moss, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for David Tsao
ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)