BillionToOne holder plans $171K stock sale

Rule 144 notice details planned sale of 1,750 BLLN Class A shares plus recent trust account sales by stakeholder David Tsao.

Rhea-AI Filing Summary

BillionToOne, Inc. (BLLN) has a notice of proposed sale of restricted or control securities under Rule 144 for the account of David Tsao. The filing covers up to 1,750 Class A shares of BillionToOne, held at Fidelity Brokerage Services LLC, with an aggregate market value of $170,695.00, and an intended sale date of September 9, 2026 on NASDAQ. The notice also lists prior Rule 144 sales over the past three months by David Tsao and the Dt 2021 Irrevocable Trust, including 20,000 Class A shares sold for $2,045,326.00 and 3,500 shares for $355,145.00 on June 15, 2026. A remark states that today’s sale and those prior sales occurred in the Dt 2021 Irrevocable Trust account managed by Icontrust LLC as trustee, with Tsao as an account stakeholder.

Key Figures

Shares proposed for sale: 1,750 Class A shares Aggregate market value of proposed sale: $170,695.00 Intended sale date: September 9, 2026 +4 more

7 metrics

Shares proposed for sale 1,750 Class A shares Securities to be sold under Rule 144 for BillionToOne, Inc.

Aggregate market value of proposed sale $170,695.00 Value of 1,750 Class A shares listed in the notice

Intended sale date September 9, 2026 Date associated with proposed Rule 144 sale of 1,750 shares

Sale on June 15, 2026 (Tsao) 20,000 Class A shares for $2,045,326.00 Listed in securities sold during the past 3 months

Sale on June 15, 2026 (Trust) 3,500 Class A shares for $355,145.00 Dt 2021 Irrevocable Trust transaction

Sale on July 13, 2026 (Tsao) 20,000 Class A shares for $2,497,697.77 Additional sale in past 3 months table

Sale on August 10, 2026 (Tsao) 10,000 Class A shares for $928,600.00 Sale listed in past 3 months table

Key Terms

Rule 144, Irrevocable Trust, attorney-in-fact

3 terms

Rule 144 regulatory

"See the definition of "person" in 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.

Irrevocable Trust financial

"Dt 2021 Irrevocable Trust 1035 OBrien Drive Menlo Park CA 94025 | Class A"

An irrevocable trust is a legal arrangement where an owner transfers assets into a separate entity managed by a trustee and gives up the power to modify or reclaim those assets. For investors it matters because putting stock or other holdings into such a trust can change who controls and benefits from the assets, affect taxes and creditor protection, and influence how easy it is to sell or value those holdings—like placing valuables in a locked safe overseen by someone else.

attorney-in-fact regulatory

"as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for David Tsao."

An attorney-in-fact is the person or entity given legal authority through a power of attorney to act on behalf of another for specific tasks, such as signing documents, voting shares, or handling transactions. For investors, this matters because it lets a trusted representative make timely decisions or complete paperwork when the owner cannot, much like handing keys to someone to run errands on your behalf—so checks on scope and limits of that authority are important.

FAQ

What does the Form 144 filing mean for BillionToOne, Inc. (BLLN)?

It is a Rule 144 notice that David Tsao, through a broker and trust account, may sell 1,750 Class A shares of BillionToOne, Inc. with an aggregate market value of $170,695.00, in addition to sales already made in the past three months.

How many BLLN shares are proposed to be sold in this new notice?

The notice covers a proposed sale of 1,750 Class A shares of BillionToOne, Inc., with an aggregate market value of $170,695.00, to be sold through Fidelity Brokerage Services LLC on or after September 9, 2026.

What BLLN shares has David Tsao sold in the last three months?

The filing lists multiple sales of Class A shares, including 20,000 shares for $2,045,326.00 and 3,500 shares for $355,145.00 on June 15, 2026, plus additional 20,000, 10,000, and 3,500-share transactions on later dates with stated dollar proceeds.

Who is actually executing the recent BLLN share sales reported for David Tsao?

The remark states that today’s sale and the past three months’ sales occurred in the Dt 2021 Irrevocable Trust account, with Icontrust LLC as trustee on the account and David Tsao as an account stakeholder.

Which broker is handling the proposed BLLN share sale under this Form 144?

The proposed sale of 1,750 Class A shares of BillionToOne, Inc. is listed in an account at Fidelity Brokerage Services LLC, which is also named in the signature block through a duly authorized representative acting as attorney-in-fact for David Tsao.

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

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Available on EDGAR 09/09/2026 - 12:21 PM Accepted by SEC EDGAR 09/09/2026 - 12:20 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	1750	170695.00	42644388	09/09/2026	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	12/30/2021	Pre IPO Shares	Issuer			1750	12/30/2021	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 OBrien Drive Menlo Park CA 94025	Class A	06/15/2026	20000	2045326.00
Dt 2021 Irrevocable Trust 1035 OBrien Drive Menlo Park CA 94025	Class A	06/15/2026	3500	355145.00
David Tsao 1035 OBrien Drive Menlo Park CA 94025	Class A	07/13/2026	20000	2497697.77
Dt 2021 Irrevocable Trust 1035 OBrien Drive Menlo Park CA 94025	Class A	07/13/2026	3500	439110.00
David Tsao 1035 OBrien Drive Menlo Park CA 94025	Class A	08/10/2026	10000	928600.00
Dt 2021 Irrevocable Trust 1035 OBrien Drive Menlo Park CA 94025	Class A	08/10/2026	3500	325010.00
David Tsao 1035 OBrien Drive Menlo Park CA 94025	Class A	08/25/2026	10000	1000000.00

144: Remarks and Signature

Remarks	Todays sale and sales within the past 3 months 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	09/09/2026
Date of Plan Adoption or Giving of Instruction, If Relying on Rule 10b5-1	06/08/2026
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/ Jessica Spraker, 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)