Company: BLLN
Filing Date: 2025-10-17
Form Type: S-1/A
Source: 0001193125-25-242632
Chunk: 333

Company: BillionToOne, Inc.
Filing Date: 2025-10-17
Form: S-1/A
Chunk 333
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 Regulatory Authority (FSRA) or the Dubai Financial Services Authority (DFSA). Notice to prospective investors in Australia This prospectus:

| • |     | does not constitute a disclosure document or a prospectus under Chapter 6D.2 of the Corporations Act 2001 (Cth) (the 
 Corporations Act);                                                                                                   |

| • |     | has not been, and will not be, lodged with the Australian Securities and Investments Commission (ASIC), as a disclosure                                                           
 document for the purposes of the Corporations Act and does not purport to include the information required of a disclosure document for the purposes of the Corporations Act; and |

| • |     | may only be provided in Australia to select investors who are able to demonstrate that they fall within one or more of the 
 categories of investors, available under section 708 of the Corporations Act (Exempt Investors).                           |

The shares may not be directly or indirectly offered for subscription or purchased or sold, and no invitations to subscribe for or buy the shares may be issued, and no draft or definitive offering memorandum, advertisement or other offering material relating to any shares may be distributed in Australia, except where disclosure to investors is not required under Chapter 6D of the Corporations Act or is otherwise in compliance with all applicable Australian laws and regulations. By submitting an application for the shares, you represent and warrant to us that you are an Exempt Investor. As any offer of shares of our Class A common stock under this prospectus will be made without disclosure in Australia under Chapter 6D.2 of the Corporations Act, the offer of those securities for resale in Australia within 12 months may, under section 707 of the Corporations Act, require disclosure to investors under Chapter 6D.2 if none of the exemptions in section 708 applies to that resale. By applying for the shares of our Class A common stock you undertake to us that you will not, for a period of 12 months from the date of issue of the shares, offer, 245

transfer, assign or otherwise alienate those shares of our Class A common stock to investors in Australia except in circumstances where disclosure to investors is not required under Chapter
6D.2 of the Corporations Act or where a compliant disclosure document is prepared and lodged with ASIC.

Notice to prospective investors in Japan

The shares have not been and will not be registered pursuant to Article 4, Paragraph 1 of the Financial Instruments and Exchange Act. Accordingly, none of the shares nor