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What an 8-K and an S-1 are

Two US securities filings appear again and again in exit records. The 8-K reports major events at a listed company, such as signing or completing a deal. The S-1 is the registration statement a company uses to register securities with the SEC, most often before an IPO.

• Form 8-K is known as a current report. It is the report public companies must file with the SEC to announce major events that shareholders should know about.¹
• Companies generally have four business days after a triggering event to file an 8-K.¹
• In practice, acquirers often file an 8-K when they sign a merger agreement (Item 1.01, entry into a material definitive agreement) and again when the deal closes. Facebook's 8-K of 19 February 2014 on WhatsApp listed Item 1.01 and attached the press release as Exhibit 99.1.²
• Form S-1 is used for registration under the Securities Act of 1933 by issuers for which no other form is prescribed, and its front part and prospectus cover must follow Item 501 of Regulation S-K.³
• The S-1 prospectus includes summary information and risk factors, the use of proceeds and a description of the business. The final priced prospectus is then filed with the SEC, as with Alibaba's 2014 prospectus on Form 424B4.^3,4

Sources

1. US Securities and Exchange Commission (Investor.gov), Glossary: Form 8-K (28 October 2026)
2. US Securities and Exchange Commission (EDGAR), Facebook Inc. Form 8-K filing index, 19 February 2014 (19 February 2014)
3. US Securities and Exchange Commission, Form S-1 general instructions (28 October 2026)
4. US Securities and Exchange Commission (EDGAR), Alibaba Group Holding Ltd prospectus (Form 424B4) (22 September 2014)