What Is an S-1? Form S-1 Definition, How It Works and Examples

US law says a company may not offer or sell shares to the public unless the offer is registered with the SEC or an exemption applies. The S-1 SEC filing is how most companies register. The form’s own instructions say it is used by any company for which no other form is authorized. A foreign private issuer, a company based abroad that meets the SEC’s test, files the similar Form F-1.

The S-1 is a living document. The company files changes as amendments, marked S-1/A on EDGAR, as the SEC staff comments and as the deal takes shape. Once the SEC declares it effective, the company usually files a final prospectus with the offer price, listed as 424B4 or 424B3.

An S-1 is used mostly for an IPO, but it is not limited to one. A company can also use it to register shares that existing holders want to resell. Coinbase did that for its direct listing in 2021.

The S-1 form is short. It is mostly a list of items, each pointing to a rule in Regulation S-K, the SEC’s rulebook for disclosure. The answers to those items make up the document, and most of it is the prospectus. The SEC estimates the form takes about 160 hours to complete.

The financial statements follow Regulation S-X, the SEC’s accounting rulebook. Most companies show three years of audited statements. An emerging growth company or a smaller reporting company may show two. The S-1 must be signed by the company, its chief executive, its finance and accounting chiefs and a majority of its board.

1. 01
   Confidential draftSince 2017, any company may first submit a draft for private review by the SEC staff.
2. 02
   Public filingThe S-1 and the earlier drafts become public at least 15 days before the roadshow, the series of pitches to investors.
3. 03
   SEC commentsThe staff checks the disclosure against the rules and sends comment letters. The company answers with amendments. The letters go public on EDGAR at least 20 business days after the S-1 takes effect.
4. 04
   Preliminary prospectusA version with a price range goes to investors. Its cover carries a legend saying the information is not complete and may change. Bankers call it the red herring.
5. 05
   EffectivenessBy law, an S-1 takes effect 20 days after filing. Companies add a delaying amendment so that the SEC sets the date instead, once its review ends.
6. 06
   Final prospectusThe price can be left out at effectiveness. It then appears in a final prospectus filed within 15 business days.

The SEC does not judge whether the company is a good investment. Its investor bulletin says the staff does not evaluate the merits of any IPO. Responsibility for complete and accurate disclosure lies with the company and the others who prepare the document. The full sequence of an IPO is on how IPOs work.

Take a company that registers up to $500M of shares. The company, its numbers and its price are illustrative. Two figures from its S-1 show how the document turns rules into money.

The dilution section is where an S-1 compares buyers. New investors pay $20.00 for a share backed by $6.00 of net assets. Early holders paid $2.50 on average. The SEC bulletin calls this gap usually significant, and the table puts a number on it.

If you own shares or options in the company, the S-1 answers questions the company may never have answered in private. Four places are worth reading first.

• Principal stockholdersWho holds large stakes, before and after the offering.
• Recent sales of unregistered securitiesEvery private round and employee grant from the past three years, with the exemption used, such as Rule 701 for employee equity.
• Underwriting or plan of distributionThe bank fee and the IPO lock-up that sets when existing holders may sell.
• Shares eligible for future saleHow many shares become sellable and when, under the lock-up and Rule 144.

Read the latest version. Each S-1/A replaces parts of the last one, and the price range, the share count and the lock-up can all change before pricing.

• Reading the S-1 as SEC approvalThe staff reviews disclosure. It does not judge the merits of the offering.
• Reading an old versionAmendments change the range, the share count and the terms. Check the newest S-1/A or the final prospectus.
• Treating the price range as the priceThe range is an estimate. The final price is set at pricing and can land outside it.
• Assuming a filing means an IPO dateA company can file and then wait for months or call the offering off.
• Skipping Part IIRecent unregistered sales and the exhibits sit in Part II, outside the prospectus.

Form S-1

The SEC registration statement for a public offering by a US company when no other form applies.

Registration statement

The filing that registers an offer of securities with the SEC. It includes the prospectus.

Prospectus

The part of the registration statement investors read: business, risks, financials and offer terms.

S-1/A

An amendment to Form S-1, filed as the document changes before effectiveness.

EDGAR

The SEC’s public database of filings, free to search.

Foreign private issuer

A company based outside the US that meets the SEC’s test. It registers on Form F-1.

Price range

The estimated range for the offer price shown in the preliminary prospectus.

Red herring

The preliminary prospectus, named for the legend saying it is incomplete and may change.

Delaying amendment

A statement that keeps the S-1 from taking effect automatically after 20 days.

Dilution

The gap between the offer price and the book value per share after the offering.

Figures were last checked on October 21, 2026. The rules are United States federal rules. The SEC fee rate changes every fiscal year, on October 1.