Prospectus Supplements (424B)
The filing that sets the final terms of an actual sale under an existing registration. When a stock gaps down overnight on an offering, this is usually the document.
MadStockAlerts Research · Updated August 28, 2026
What to take away
- A 424B contains the concrete terms: price, size, underwriters and use of proceeds.
- It is filed at pricing, so it appears after the market has learned of the deal.
- The suffix number indicates which rule the filing is made under.
- Selling stockholder tables show whether the company or existing holders are selling.
- A 424B means securities were actually sold; a shelf only means they could be.
MAD Academy Training Video · 0:45
The Offering, Priced and Final
A 424B is the filing that says an offering actually happened, at what price and in what size — the details the announcement leaves out.
This lesson is part of a Stock Alerts + Tools plan.
Where it sits in the sequence
- 1The shelfAn S-3 shelf registration registers a dollar amount of securities for future sale.
- 2The launchThe company announces an offering, usually after the close.
- 3PricingThe deal prices overnight, typically at a discount to the last close.
- 4The 424BThe prospectus supplement is filed with the final terms.
The discount at step three is the mechanism behind the overnight price gap. Underwriters have to clear a large block, and the buyers taking it require compensation for doing so; the discount is that compensation and it repricess the whole security.
- 1S-3 shelfRegisters an amount for sale at some later date
- 2LaunchAnnounced, usually after the close
- 3PricingPriced overnight, typically at a discount
- 4424B filedFinal terms on the record
What to read in it
- Price per share, and the discount to the prior close.
- Number of shares, and the same figure as a percentage of shares outstanding.
- Whether the shares are primary, secondary, or a mix.
- The over-allotment option, which allows underwriters to sell additional shares.
- Use of proceeds, stated with varying degrees of specificity.
- Any concurrent transactions, such as a debt repayment tied to the raise.
The second is the one to compute rather than read. Fifteen million shares means nothing until it is set against the count outstanding; at three hundred million shares it is five percent dilution and at thirty million it is fifty.
The suffixes
| Form | Filed under |
|---|---|
| 424B1 / 424B2 | Rules covering prospectuses omitting pricing information |
| 424B3 | Prospectus containing substantive changes or additions |
| 424B4 | The common form for a priced underwritten offering |
| 424B5 | Supplement to a shelf, the usual form for a follow-on |
The exact rule matters less than knowing that a 424B appearing on a company's index means securities were actually sold, as distinct from a shelf filing which only means they could be.
Use of proceeds, read sceptically
The use-of-proceeds section ranges from specific to close to meaningless. General corporate purposes, which may include working capital and capital expenditures is a standard formulation and tells a reader nothing beyond the fact that no specific use was committed to.
Specificity is informative in both directions. A stated intention to repay a named facility is checkable against the next balance sheet; a vague statement in a company that is burning cash says the raise was about survival rather than opportunity.
The terms that determine the effect on holders
A prospectus supplement is where an offering's actual terms appear, and a small number of them decide what the transaction does to existing holders.
| Term | What to look for |
|---|---|
| Size, in shares and dollars | As a percentage of shares outstanding, which is the dilution |
| Price against the market | The discount to the last close, which is what the buyers required |
| Warrants attached | Additional dilution at a fixed price, exercisable later |
| Who is selling | The company raising money, or existing holders exiting |
| Lock-up on the company | Whether more can be sold immediately afterwards |
| Use of proceeds | General corporate purposes says the least of any answer available |
The fourth row changes the meaning entirely. A primary offering brings cash into the business and dilutes holders; a secondary offering brings cash to selling shareholders and dilutes nobody, while telling you something about what those holders think. Many deals are a mix, and the split is stated.
A registered direct offering with warrants attached, priced at a discount, is a structure most often used by companies with limited alternatives. Nothing about it is improper, and the terms describe the negotiating position the company was in.
How the offering reaches the market
The structure of an offering determines who takes the risk and what it costs, and the terms differ enough that the same headline size can mean quite different things.
| Structure | Who takes the risk | Character |
|---|---|---|
| Firm commitment underwriting | The underwriters, who buy the shares | The standard for a sizeable deal |
| Best efforts | The company, since nothing is guaranteed | Common where demand is uncertain |
| Registered direct | Negotiated with specific investors | Fast, often discounted, frequently with warrants |
| At-the-market | Sold gradually into the market | No single print, no announcement, no discount |
| Rights offering | Existing holders, who are offered first | Preserves proportional ownership for those who participate |
The last row is the structure that treats existing holders best and is rare in US markets. A rights offering gives current holders the opportunity to buy at the offer price, so anyone who participates is not diluted, and anyone who does not can usually sell the right.
The underwriting discount, stated on the cover, is what the syndicate is paid. It is a few percent on a large deal and considerably more on a small or difficult one, and it is a direct read on how hard the offering was to place.