What is a 424B5? Reading the prospectus supplement behind a shelf takedown
A 424B5 is where shelf capacity turns into a specific deal. Learn its layout, the six numbers to pull, and why one shelf can produce very different 424B5s.
The name, decoded
424B5 is the EDGAR form type for a prospectus filed under Securities Act Rule 424(b)(5). In practice it is most often a prospectus supplement: a document that adds the specific terms of one offering to a base prospectus that is already part of an effective shelf registration statement.
Lesson 5 showed the sequence: a Form S-3 shelf is filed, becomes effective, and creates registered capacity. Nothing has been sold. The 424B5 is usually the first document that says what is being sold, how much, how, and at what price or pricing method.
Rule 424(b)(5) covers a prospectus that carries both shelf-offering information and other substantive changes. It is generally due within two business days after the offering price is set or the prospectus is first used. So a 424B5 often appears on EDGAR the morning after an overnight pricing, sometimes after the deal was already announced in a press release.
Where 424B5 sits among its siblings
Rule 424(b) has several paragraphs, and EDGAR labels each one as its own form type. The ones a dilution reader meets most often:
| Form type | Typical use | Reading tip |
|---|---|---|
| 424B5 | Shelf information plus other substantive changes: most small-cap shelf takedowns and ATM prospectuses | The offering-specific document for most small-cap shelf deals |
| 424B2 | Shelf takedown information without other substantive changes | Seen more with large issuers and debt programs |
| 424B4 | Final prospectus after pricing in a non-shelf deal (Rule 430A information plus changes) | Common in IPOs and S-1 offerings |
| 424B3 | Other substantive changes; very often a resale prospectus | Check who sells: the company, or selling stockholders? |
| 424B7 | Adds selling-stockholder names and amounts previously omitted | Resale, not company issuance |
The labels are filing mechanics, not deal types. The cover page tells you what the deal actually is.
The layout, page by page
Most 424B5 supplements follow the same order. The cover alone answers most questions:
- Cover page. Registration number, base prospectus date, security, amount or ceiling, price or pricing method, agent or underwriter, last reported price and its date, expected delivery date. Smaller issuers may add a General Instruction I.B.6 paragraph (Lesson 15).
- Prospectus supplement summary and The Offering: shares offered, shares outstanding after the offering, and the base date used for that count.
- Risk factors, often including offering-specific risks.
- Use of proceeds.
- Dilution: the change in net tangible book value per share. This is an accounting measure, not the ownership dilution from Lesson 1.
- Plan of distribution: fees, lock-ups, standstill periods, and whether an agent or underwriter is involved.
Behind the supplement you will find the base prospectus, with generic descriptions of every security the shelf could ever cover. The supplement controls where they differ.
The six numbers to pull from any 424B5
| # | Number | Where it usually is |
|---|---|---|
| 1 | Security type and amount, or program ceiling | Cover |
| 2 | Price, or how price will be set | Cover |
| 3 | Shares outstanding before, and its as-of date | "The Offering" footnote |
| 4 | Shares outstanding after, and its assumption | "The Offering" |
| 5 | Excluded potential shares (options, warrants, convertibles) | "The Offering" footnote |
| 6 | Fees and other offering costs | Cover table, plan of distribution |
Numbers 3 and 4 are the trap. The "before" figure is often weeks or months old, and the "after" figure may assume a price or assume warrant exercise.
Walkthrough: one shelf, two very different 424B5s
Company: CapsoVision, Inc. Checked through October 5, 2026. Figures are quoted or derived from the linked filings.
The shelf: a Form S-3 (Registration No. 333-298315) filed August 13, 2026, declared effective August 21, 2026.
424B5 number 1: an ATM program
- Up to $100,000,000 of common stock through a sales agent under a sales agreement dated August 13, 2026, in "at the market" sales under Rule 415(a)(4).
- Agent compensation up to 3.0% of gross proceeds.
- Last reported price on August 12, 2026: $6.86.
- "The Offering": up to 64,609,407 shares outstanding after the offering, assuming 14,577,259 shares sold at $6.86, starting from 50,032,148 shares outstanding as of June 30, 2026.
Check the assumption: $100,000,000 ÷ $6.86 ≈ 14,577,259. That share count is an illustration at one price. At a lower price the same dollar ceiling buys more shares. And on August 21 nothing had been sold. Lesson 6 explains how to reconcile actual ATM sales period by period.
424B5 number 2: a priced direct sale
424B5 dated September 17, 2026, filed September 18, 2026, labeled "Prospectus Supplement (To Prospectus dated August 21, 2026)".
- 3,163,444 shares at $5.69 per share, sold directly to existing stockholders under a securities purchase agreement dated September 17, 2026. Two of the investors are disclosed as related persons through their holdings above 5%.
- No underwriter or placement agent, so no commissions. Gross proceeds about $18.0 million, net about $17,834,500.
- Price context: last reported price on September 16, 2026 was $5.99; the supplement describes $5.69 as about a 5% discount.
- "The Offering": 53,195,592 shares outstanding after the offering, again based on 50,032,148 as of June 30, 2026.
Now read the footnote. It also lists 149,953 shares issued after June 30, 2026 under the ATM program as excluded from that base. So the September supplement itself tells you the ATM had started selling, and that its "after" figure is understated by those shares:
50,032,148 + 3,163,444 + 149,953 = 53,345,545 (our arithmetic, still before any later ATM sales, option exercises, or other issuance)
What the pair teaches
| 424B5 of August 21 | 424B5 of September 18 | |
|---|---|---|
| Deal type | ATM program | Priced direct sale |
| Amount | Up to $100 million ceiling | 3,163,444 shares, fixed |
| Price | Market, sale by sale | $5.69, fixed |
| Share change on filing date | None | Delivery expected September 18 |
| How you learn actual sales | Later reports and supplements | The supplement and closing 8-K |
Same company, same shelf, same form type, completely different effects on the share count.
Five reading habits
- Read the cover line under the title: "Prospectus Supplement (To Prospectus dated ...)" tells you the base prospectus and shelf.
- Write down every as-of date before writing down any share count.
- Recompute any assumed-price share count, and note the price date.
- Read the "excludes" list in The Offering. It is a free inventory of potential shares, and sometimes of recent ATM sales.
- Pair the 424B5 with the Form 8-K filed around the same day; the 8-K attaches the agreement.
Remember one line
A 424B5 turns shelf capacity into a specific offering; the cover tells you which kind, and the footnotes tell you how stale the share count is.