What is a 424B prospectus?

A 424B is the final prospectus a company files with the SEC after its registration statement (such as an S-1 or S-3) is declared effective. It contains the completed terms of a securities offering — the actual price, number of shares, and use of proceeds. The number suffix (424B1 through 424B5) indicates what was finalized after the earlier filing.

Where a 424B fits

A registration statement like an S-1 (for an IPO) or S-3 (for follow-on offerings by established companies) registers securities, but it often leaves final pricing blank while the SEC reviews it. Once the registration is effective and the deal prices, the company files the definitive prospectus as a Form 424B. This is the document with the real, locked-in terms — so for any priced offering, the 424B is the authoritative version to read.

The B-number variants

The suffix tells you what was completed relative to the effective registration statement. The most common are 424B1 and 424B2 (prospectuses that include pricing or other information omitted earlier), 424B3 (a prospectus filed under Rule 424(b)(3), often for updates), 424B4 (the classic final IPO prospectus reflecting the priced deal), and 424B5 (typically a prospectus supplement for a takedown off an existing shelf registration). You do not need to memorize the differences — the key point is that a 424B carries final offering terms.

How to use it

If you are researching an IPO or a secondary offering after it has priced, go straight to the 424B for the offering price, share count, underwriters, and use of proceeds. Pair it with the underlying S-1 or S-3, which carries the fuller business description, risk factors, and financial statements. A wave of 424B5 filings by a company can also signal it is repeatedly tapping the market for capital — worth noting for dilution.

Related questions

What is a Form S-1 (IPO registration statement)?

A Form S-1 is the registration statement a company files with the SEC to go public. It is the core disclosure document for an IPO, containing the business description, risk factors, audited financials, how the proceeds will be used, and ownership details. The prospectus that investors read is part of the S-1.

10-K vs 10-Q: what's the difference?

A 10-K is a company's comprehensive annual report; a 10-Q is a shorter quarterly report filed for the first three quarters of the year. The 10-K is audited and far more detailed; the 10-Q is unaudited (reviewed) and updates investors on recent quarterly performance. There is no fourth 10-Q because the 10-K covers the final quarter.

How do I read the Risk Factors section of a 10-K?

Read a 10-K's Risk Factors (Item 1A) to find what management believes could hurt the business. Focus on company-specific risks over generic boilerplate, note the order (most material tends to come first), and compare against the prior year to spot newly added risks — those additions are often the most telling.

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