Company: BLLN
Filing Date: 2025-06-20
Form Type: DRS
Source: 0000950123-25-006095
Chunk: 3

Company: BillionToOne, Inc.
Filing Date: 2025-06-20
Form: DRS
Chunk 3
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 a description of the compensation payable to the underwriters. |

At our request, the underwriters have reserved up to 5% of the shares of Class A common stock being offered by this prospectus for sale, at the initial public offering price, to our officers, directors and employees through a directed share program. See the section titled “Underwriting – Directed share program.” We have granted the underwriters an option for a period of 30 days to purchase up to additional shares of Class A common stock. Investing in our Class A common stock involves a high degree of risk. See “ Risk factors” beginning on page 19. Neither the Securities and Exchange Commission nor any other state securities commission has approved or disapproved of these securities or passed on the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense. The underwriters expect to deliver the shares to purchasers on or about , 2025.

| J.P. Morgan |     | Piper Sandler          |     | Jefferies |     | William Blair |
| Stifel      |     | Wells Fargo Securities |     |           |     | BTIG          |

, 2025

### EXPLANATORY NOTE
Pursuant
to the applicable provisions of the Fixing America’s Surface Transportation Act, we are omitting our unaudited financial statements as of and for the three months ended March 31, 2025 and 2024. While this financial information is otherwise
required by Regulation S-X, we reasonably believe that it will not be required to be included in the prospectus at the time of the contemplated offering. We intend to amend this registration
statement to include all financial information required by Regulation S-X at the date of such amendment before distributing a preliminary prospectus to investors.

Table of contents

|                                                                                       |     | Page |     |
| Letter from our co-founder and                                                        
 CEO                                                                                   |     |      |   i |
| Glossary                                                                              |     |      |  ii |
| Prospectus summary                                                                    |     |      |   1 |
| Risk factors                                                                          |     |      |  19 |
| Special note regarding forward-looking statements                                     |     |      |  76 |
| Market, industry and other data                                                       |     |      |  78 |
| Use of proceeds                                                                       |     |      |  79 |
| Dividend policy                                                                       |     |      |  80 |
| Capitalization                                                                        |     |      |  81 |
|