Key facts
- This page summarizes David Tsao's Form 4 filing for BillionToOne, Inc. (BLLN).
- 15 reported transactions and 2 derivative rows are listed below.
- Accepted by SEC: 07 Oct 2026, 19:56.
David Tsao - 05 Oct 2026 Form 4 Insider Report for BillionToOne, Inc. (BLLN)
- Reporting relationship
- Chief Technology Officer, Director
- Issuer ticker
- BLLN
- Reported as of
- 05 Oct 2026
- Net transaction value
- -$2,162,950
- SEC form
- 4
- Accepted by SEC
- 07 Oct 2026, 19:56:35 UTC
- Prior SEC filing
- 28 Sep 2026
- Source filing
- View source filing
- Reporting owner signature
- /s/ Thomas P. Lynch, Attorney-in-Fact
Source evidence
Original filing metadata and source links for verification.
4 source fields
Reporting owner
1 detail
Key filing fact
David Tsao filed Form 4 for BillionToOne, Inc. (BLLN) on 07 Oct 2026.
Change
- Previous filing in this sequence was filed on 28 Sep 2026.
- Current net transaction value: -$2,162,950.
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
View source filing
Ownership activity is grounded in SEC Form 4 disclosures.
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
- 07 Oct 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
- 05 Oct 2026
- Ownership
- Direct
- Footnotes
- F1
BLLN
transaction
Class A Common Stock
Options Exercise
- Transaction value
- Shares
- +10,000
- Change %
- +91%
- Price
- $2.80*
- Shares after
- 21,000
- Date
- 05 Oct 2026
- Ownership
- Direct
- Footnotes
- F1
BLLN
transaction
Class A Common Stock
Sale
- Transaction value
- $91,710
- Shares
- -866
- Change %
- -4.1%
- Price
- $105.90
- Shares after
- 20,134
- Date
- 05 Oct 2026
- Ownership
- Direct
- Footnotes
- F1, F2
BLLN
transaction
Class A Common Stock
Sale
- Transaction value
- $204,635
- Shares
- -1,909
- Change %
- -9.5%
- Price
- $107.20
- Shares after
- 18,225
- Date
- 05 Oct 2026
- Ownership
- Direct
- Footnotes
- F1, F3
BLLN
transaction
Class A Common Stock
Sale
- Transaction value
- $464,356
- Shares
- -4,284
- Change %
- -24%
- Price
- $108.39
- Shares after
- 13,941
- Date
- 05 Oct 2026
- Ownership
- Direct
- Footnotes
- F1, F4
BLLN
transaction
Class A Common Stock
Sale
- Transaction value
- $318,398
- Shares
- -2,921
- Change %
- -21%
- Price
- $109.00
- Shares after
- 11,020
- Date
- 05 Oct 2026
- Ownership
- Direct
- Footnotes
- F1, F5
BLLN
transaction
Class A Common Stock
Sale
- Transaction value
- $2,202
- Shares
- -20
- Change %
- -0.18%
- Price
- $110.08
- Shares after
- 11,000
- Date
- 05 Oct 2026
- Ownership
- Direct
- Footnotes
- F1
BLLN
transaction
Class A Common Stock
Sale
- Transaction value
- $58,585
- Shares
- -555
- Change %
- -5%
- Price
- $105.56
- Shares after
- 10,445
- Date
- 05 Oct 2026
- Ownership
- Direct
- Footnotes
- F1, F6
BLLN
transaction
Class A Common Stock
Sale
- Transaction value
- $42,442
- Shares
- -400
- Change %
- -3.8%
- Price
- $106.10
- Shares after
- 10,045
- Date
- 05 Oct 2026
- Ownership
- Direct
- Footnotes
- F1, F7
BLLN
transaction
Class A Common Stock
Sale
- Transaction value
- $236,435
- Shares
- -2,200
- Change %
- -22%
- Price
- $107.47
- Shares after
- 7,845
- Date
- 05 Oct 2026
- Ownership
- Direct
- Footnotes
- F1, F8
BLLN
transaction
Class A Common Stock
Sale
- Transaction value
- $533,554
- Shares
- -4,916
- Change %
- -63%
- Price
- $108.53
- Shares after
- 2,929
- Date
- 05 Oct 2026
- Ownership
- Direct
- Footnotes
- F1, F9
BLLN
transaction
Class A Common Stock
Sale
- Transaction value
- $199,625
- Shares
- -1,829
- Change %
- -62%
- Price
- $109.14
- Shares after
- 1,100
- Date
- 05 Oct 2026
- Ownership
- Direct
- Footnotes
- F1, F10
BLLN
transaction
Class A Common Stock
Sale
- Transaction value
- $11,009
- Shares
- -100
- Change %
- -9.1%
- Price
- $110.09
- Shares after
- 1,000
- Date
- 05 Oct 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 %
- -1.8%
- Price
- $2.80*
- Shares after
- 546,667
- Date
- 05 Oct 2026
- Ownership
- Direct
- Underlying class
- Class A Common Stock
- Underlying amount
- 10,000
- Exercise price
- $2.80
- Footnotes
- F11
BLLN
transaction
Derivative
Stock Option (right to buy)
Options Exercise
- Transaction value
- Shares
- -10,000
- Change %
- -1.8%
- Price
- $2.80*
- Shares after
- 536,667
- Date
- 05 Oct 2026
- Ownership
- Direct
- Underlying class
- Class A Common Stock
- Underlying amount
- 10,000
- Exercise price
- $2.80
- Footnotes
- F11
* 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 11 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 June 5, 2026.
Footnote F2
The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $105.505 to $106.350 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.
Footnote F3
The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $106.730 to $107.700 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.
Footnote F4
The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $107.7354 to $108.710 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.
Footnote F5
The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $108.740 to $109.480 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.
Footnote F6
The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $104.880 to $105.720 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.
Footnote F7
The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $105.890 to $106.180 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.
Footnote F8
The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $107.010 to $107.970 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.
Footnote F9
The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $108.040 to $109.030 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.
Footnote F10
The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $109.040 to $109.500 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.
Footnote F11
The options are fully vested and exercisable.