Confidential IPO Filing Explained: Why Anthropic’s Draft S-1 Is Still Private

Anthropic submitted its draft S-1 to the SEC confidentially in June, yet its figures keep appearing in the press. How the nonpublic review process works, the 15-day rule before a roadshow, and what founders should expect if they file the same way.

Since its brief June 1 notice that a draft S-1 had gone to the SEC in confidence, Anthropic has not released a single page of its IPO paperwork. The draft’s contents keep surfacing regardless: Reuters described the 2025 figures in late September, and on October 20 it put Anthropic’s loss for the half-year to June at $80.7 billion. The gap between a confidential IPO filing and what readers already know about it is a useful lesson in how the process works.

Where it stands: No public Anthropic S-1 had been posted by October 21. PitchBook, writing about the leaked numbers, said its figures come from reporting on the draft “because the public filing has not been posted.”

What a confidential IPO filing is

A confidential filing is a draft registration statement that the SEC staff reviews out of public view. The company and the regulator trade comments and revisions, and nothing goes on EDGAR until the company decides to file publicly.

The option is newer than many founders assume. The JOBS Act of 2012 gave it to emerging growth companies. In 2017 the SEC extended voluntary draft submissions to all issuers, and in March 2025 it broadened the accommodations again.

The SEC also says that, where possible, it will keep draft submissions and related correspondence confidential, subject to applicable law. A draft also does not have to be complete in every respect: the staff will not hold up its review if the company reasonably believes omitted financial information will not be needed when it files publicly.

The clock that starts when the draft goes public

Confidentiality has an end date built in. The SEC agrees to a private review only after the company promises, in a cover letter, to put the filing on the public record with a 15-day gap before the road show begins, or before its requested effective date when there is no road show.

Step What SEC policy says
Draft submitted Nonpublic staff review
Underwriter names May be left out of the first draft
Public filing At least 15 days before the road show
Earlier drafts Filed publicly at the same time
Comment letters Released no sooner than 20 business days after effectiveness

That makes the public S-1 a lead indicator for the marketing itself. Bloomberg reported on October 1 that Anthropic could begin marketing its IPO the week of Nov. 9. Under the 15-day rule, the public filing would have to land beforehand.

The earlier drafts become public too. When the company files, the drafts it submitted privately go on EDGAR along with the registration statement, so revisions made during the SEC review eventually become visible.

What Anthropic was allowed to say

Anthropic’s June notice was short for a reason. Rule 135 lets a company announce a planned registered offering without it counting as an offer to sell, but only if the notice stays within narrow limits. It must say it is not an offer, and it may describe the purpose of the offering only briefly, “without naming the underwriters.”

Anthropic’s announcement followed that template. It said the filing “gives us the option to go public after the SEC completes its review,” and that the number of shares and the price had not been set. The banks reported to be working on the deal have been named only by people speaking to reporters.

A quiet period also applies once a registration statement is filed. Investor.gov notes that securities laws do not define the term, and that the period lasts at least until the SEC staff declares the registration effective. Breaking the restrictions on offers is called “gun-jumping.”

Why the numbers are getting out anyway

Confidential review limits what the SEC publishes. It does not stop people who have seen a draft from describing it to reporters. Reuters said its October 20 figures came from a draft prospectus “that was reviewed by Reuters.” Al Jazeera, reporting the same loss, noted that Anthropic did not respond and that “the report on the non-public information could not be immediately verified.”

Investor meetings add a second channel. A prospective buyer sees numbers before any filing is public, and those numbers can be preliminary. When Bloomberg reported Anthropic’s second-quarter revenue in August, it warned that “the figures could be revised.” The Next Web made the broader point in September: every valuation so far “has come from people briefing reporters rather than from a prospectus.”

The result is a partial picture. Readers have the headline loss and its main driver, an accounting charge of about $72 billion tied to convertible financing, but not the notes, schedules and reconciliations a public S-1 would carry.

What changes when the S-1 is public

Once filed, the registration statement and every amendment, marked S-1/A, sit on EDGAR for anyone to read. Investors can compare the reported figures with the company’s own presentation, and reporters can quote the text instead of characterizing it.

A public filing carries no seal of approval. In the regulator’s own investor guidance, review by the SEC “is not a guarantee that a company’s disclosure is complete or accurate,” and the staff takes no view on whether the offering is a good investment.

For anyone reading the eventual document, a few sections deserve attention first: revenue recognition, customer concentration and adjusted metrics. We cover how gross versus net revenue treatment changes partner sales, what Anthropic’s two-customer concentration figure teaches, and how to present non-GAAP metrics alongside GAAP results.

Lessons for founders planning a confidential filing

  • Confidential means private from the public, not from your investors. Assume anything shown at a meeting with prospective buyers could appear in print.
  • Keep one set of numbers. Figures given to investors, the draft S-1 and any later public statement should reconcile. Differences will be noticed when the filing goes public.
  • Settle accounting policies before the first draft. Revenue recognition, the treatment of convertible instruments and the definition of any adjusted metric are hard to change mid-review.
  • Plan backward from the road show. The public filing must land at least 15 days earlier, and the SEC review before that can run through several rounds of comments.
  • Prepare for silence. Rule 135 and the quiet period leave little room to correct a leaked figure in public, so plan how you will respond before anything leaks.

The process has a visible end. When the public filing arrives, PitchBook has said it will reconcile each reported figure against the document, and the SEC’s comment letters, with Anthropic’s replies, become public once 20 business days have passed after the registration takes effect.

Frequently Asked Questions

What is a confidential IPO filing?

It is a draft registration statement, usually a draft Form S-1, that a company submits to the SEC for nonpublic staff review before filing publicly. The SEC reviews and comments on it out of public view, and the company must make the filing public before it markets the shares.

Can any company file for an IPO confidentially?

Yes, for an initial public offering. The JOBS Act of 2012 created the process for emerging growth companies, and since 2017 the SEC has accepted voluntary draft submissions from all issuers.

How long before an IPO does the S-1 have to be public?

The SEC policy for draft submissions sets a minimum of 15 days between the public filing, which must include the earlier drafts, and the start of any road show. With no road show, the 15 days run back from the requested effective date.

When did Anthropic file for its IPO?

Anthropic said on June 1 this year that a draft Form S-1 had been submitted to the SEC in confidence. As of October 21, the draft had not been made public, and the figures in circulation come from reporters who reviewed it.

Are SEC comment letters on a confidential draft ever published?

Yes. Staff comments and the company replies are posted to EDGAR, but only once the registration has been effective for 20 business days or more.

Sources

This article is general information for founders and is not accounting, legal or investment advice. How a financing instrument is accounted for depends on its exact terms; work through it with your accountant or auditor. Anthropic has not published its IPO prospectus; figures are as reported by the sources cited on the dates shown.