Company: BLLN
Filing Date: 2025-06-20
Form Type: DRS
Source: 0000950123-25-006095
Chunk: 255

Company: BillionToOne, Inc.
Filing Date: 2025-06-20
Form: DRS
Chunk 255
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 completion of this offering, the holders of shares of our Class A common stock or their permitted transferees (including,
following the Class B Stock Exchange, shares of our Class A common stock issuable upon the conversion of shares of Class B common stock), will be entitled to certain rights with respect to the registration of the offer and sale of
their shares under the Securities Act. All such shares are covered by lock-up agreements or market stand-off arrangements. Following the expiration of the lock-up and market stand-off period, registration of these shares under the Securities Act would result in the shares becoming freely tradable without restriction under the
Securities Act immediately on the effectiveness of the registration. See the section titled “Description of capital stock—Registration rights” for additional information.

Rule 10b5-1plans

After this
offering, certain of our employees, including our executive officers, and/or directors may enter into written trading plans that are intended to comply with Rule 10b5-1 under the Exchange Act. Sales under
these trading plans would not be permitted until the expiration of the lock-up agreements or market stand-off arrangements relating to the offering described above.

202

Material U.S. federal income tax consequences to non-U.S.holders of our Class A common stock The following is a general discussion of the material U.S. federal income tax considerations applicable to non-U.S.holders (as defined below) with respect to their ownership and disposition of shares of our Class A common stock issued pursuant to this offering. All prospective non-U.S.holders of our Class A common stock should consult their tax advisors with respect to the U.S. federal, state, local and non-U.S.tax consequences of the purchase, ownership and disposition of our Class A common stock. For purposes of this discussion, a non-U.S.holder means a beneficial owner of our Class A common stock (other than an entity or arrangement that is treated as a partnership or pass-through entity for U.S. federal income tax purposes) that is not, for U.S. federal income tax purposes, any of the following:

| • |     | an individual citizen or resident of the United States; |

| • |     | a corporation (or other entity treated as a corporation for U.S. federal income tax purposes) created or organized in the 
 United States or under the laws of the United States, any state thereof or the District of Columbia;                      |

| • |     | an estate, the income of which is includable in gross income for U.S