# Form 424B prospectus

> A prospectus filed with the SEC under Rule 424(b), typically the final pricing terms of an IPO or a takedown from a shelf registration.

Source: https://www.quantisnow.com/glossary/form-424b
Topic: Glossary / SEC filings
Also known as: 424B, 424B prospectus, 424B5, 424B4, prospectus supplement
Last updated: 2026-10-27

A Form 424B prospectus is a prospectus or prospectus supplement filed with the SEC under Rule 424(b) of the Securities Act. It is how companies publish the final terms of a registered offering, such as the price of an IPO or the size and price of a sale from a shelf registration.

## How it works

The suffix number refers to the paragraph of Rule 424(b) the filing relies on. The ones traders see most often:

| Filing | Typical use |
|---|---|
| 424B4 | Final prospectus with pricing for a non-shelf offering, such as many IPOs |
| 424B5 | Prospectus supplement for a shelf takedown, including ATM programs |
| 424B2 | Shelf takedowns, common for debt and structured notes |
| 424B3 | Updates with substantive changes, often for resale registrations |
| 424B7 | Adds selling shareholder information to a shelf |

A final 424(b) prospectus is generally due no later than the second business day after pricing or first use. In shelf offerings, a "preliminary" 424B5 is often filed before the deal prices (sometimes after the close), and a final 424B5 follows with the price.

## Why it matters for traders

For public companies, a 424B5 is usually the moment a shelf becomes actual [dilution](https://www.quantisnow.com/glossary/dilution). The filing shows the number of shares, price per share, discount to the market, warrants, underwriter fees and use of proceeds. A preliminary 424B5 filed after 4 p.m. typically means an overnight offering, with pricing announced before the next open, often at a discount to the last close. A 424B5 tied to an [at-the-market](https://www.quantisnow.com/glossary/at-the-market-offering) program signals the company can sell into the market over time.

## Example

A hypothetical biotech, Northwind Therapeutics (NWTX), closes at $12.00. At 4:15 p.m. it files a preliminary 424B5 for an underwritten offering under its S-3 shelf. Before the open, it files a final 424B5: 8 million shares at $10.50, a 12.5% discount, raising $84 million gross. NWTX opens near $10.60.

## FAQ

### What is the difference between 424B4 and 424B5?

424B4 typically carries final pricing for non-shelf deals such as IPOs. 424B5 is commonly used for prospectus supplements in shelf offerings.

### Does a 424B filing mean new shares are being sold?

Usually, for primary offerings. A 424B3 or 424B7 for a resale registration covers existing holders selling, which does not raise cash for the company.

## Related terms

- [Form S-3](https://www.quantisnow.com/glossary/form-s-3.md): The short-form SEC registration statement seasoned public companies use to register securities, most often for shelf offerings.
- [Shelf registration](https://www.quantisnow.com/glossary/shelf-registration.md): An SEC registration that lets a company register securities in advance and sell them over time, typically up to three years, as market conditions allow.
- [Form S-1](https://www.quantisnow.com/glossary/form-s-1.md): The SEC registration statement US companies use for an IPO or other securities offering when they cannot use a shorter form such as the S-3.
- [At-the-market (ATM) offering](https://www.quantisnow.com/glossary/at-the-market-offering.md): A way for a public company to sell new shares gradually into the open market at prevailing prices through a sales agent, off a shelf registration.
- [Follow-on offering](https://www.quantisnow.com/glossary/follow-on-offering.md): A sale of additional shares by a company that is already public, used to raise more capital or let existing holders sell stock.
- [Dilution](https://www.quantisnow.com/glossary/dilution.md): The reduction in existing shareholders' ownership percentage and per-share claims on earnings when a company issues new shares.

## On Quantisnow

- [Shelf offerings and dilution](https://www.quantisnow.com/guides/shelf-offerings-and-dilution)
- [Live feed: Offerings](https://www.quantisnow.com/news/offerings)
- [Public offerings](https://www.quantisnow.com/categories/offerings)