Company: BLLN
Filing Date: 2025-10-07
Form Type: S-1
Source: 0001193125-25-233697
Chunk: 379

Company: BillionToOne, Inc.
Filing Date: 2025-10-07
Form: S-1
Chunk 379
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| Operating cash flows from financing leases (interest paid)                                     |     | $                |    140 |     | $    |    68 |

The accompanying notes are an integral part of these interim financial statements. F-43

BILLIONTOONE, INC.

Notes to Unaudited Interim Financial Statements

(1) Description of Business

BillionToOne, Inc. (the
“Company”, “we”, or “our”) was formed in 2016, and headquartered in Menlo Park, California. The Company is a precision diagnostics company that quantifies biology to create molecular diagnostics. The
Company’s proprietary molecular counting platform is designed to detect and measure DNA molecules at the single-count level to help improve disease detection. The Company currently applies the proprietary technology to non-invasive prenatal screening (“Prenatal”) and liquid biopsy (“Oncology”).

(2) Summary of Significant Accounting Policies

Basis of Presentation

The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America
(“U.S. GAAP”). Prior to April 2024, the financial statements also included the Company’s wholly owned subsidiary SeqIndia Labs Private Limited which had immaterial activities and was not material to these financial statements and
was divested in April 2024. Accordingly, during the six months ended June 30, 2024, the financial statements were consolidated while in 2025 they were not. All intercompany transactions and balances have been eliminated upon consolidation.

The Company’s significant accounting policies are discussed in “Note 2. Summary of Significant Accounting Policies” in the notes to the
financial statements as of and for the year ended December 31, 2024. There have been no significant changes to these policies during the six months ended June 30, 2025.

Unaudited interim financial information

The
unaudited financial statements do not include all disclosures, including certain notes required by GAAP on an annual reporting basis. The unaudited interim financial statements have been prepared on the same basis as the annual financial statements.
In management’s opinion, the unaudited financial statements reflect all normal recurring adjustments necessary to state fairly the balance sheets, statements of operations and comprehensive loss, of redeemable convertible preferred stock and
stockholders’ deficit, and of cash flows for the interim periods, but are not necessarily indicative of the results of operations to be anticipated for the full fiscal year or any future period.

Use of Estimates

The preparation