S-1 vs S-3
A FilingRadar Editorial guide ·
S-1
IPO Registration
Form S-1 is the SEC registration statement a company files before its IPO — the full disclosure document for new public investors.
Full S-1 definition →S-3
Shelf Registration
Form S-3 is the streamlined registration form for already-public companies — commonly used as a shelf registration for future issuances.
Full S-3 definition →Side-by-side: every attribute that matters
| Attribute | S-1 | S-3 |
|---|---|---|
| Who uses it | Companies going public for the first time; follow-on offerings by non-WKSI issuers | Seasoned public companies meeting eligibility tests (12+ months of timely SEC reporting) |
| Eligibility requirements | Any company can file (it's the default form) | Must meet float test ($75M+ public float) and reporting history; WKSIs get automatic effectiveness |
| Disclosure depth | Full prospectus — business, risk factors, financials, use of proceeds, management bios | Incorporates 10-K/10-Q/8-K by reference; shorter document |
| SEC review process | Multiple rounds of comments before effectiveness (3-9 months typical) | Automatic effectiveness for WKSIs; standard review for others |
| Use of proceeds | Disclosed specifically (one-time use) | Often generic ('general corporate purposes') — proceeds drawn down over years |
| Pricing mechanism | Single offering with disclosed range, priced via roadshow | Can be drawn down via 424B5 takedowns or ATM (at-the-market) over time |
| Dilution timing | Known upfront (offering size in S-1) | Unknown — shelf allows future issuances at company's discretion |
| Cost to company | Very expensive (legal, audit, roadshow, underwriting ~7%) | Cheaper per dollar raised; reused across multiple takedowns |
| Investor risk profile | First-time public disclosure — limited operating history visible | Established public reporting history — investor can read prior 10-Ks |
| When filed | Before an IPO or major follow-on offering | Proactively, often before any specific need to raise capital |
| Watch for as retail investor | Repeat amendments may signal SEC accounting/pricing friction | Filing of a new S-3 = company reserving the right to dilute; size matters relative to market cap |
When to read which
Read S-1 when…
When researching an IPO or a follow-on offering from a smaller, less-established public company. The S-1 prospectus is your most complete look at the business before public-market reporting begins.
Read S-3 when…
When a company you own files an S-3, especially a 'universal shelf' for ATM offerings. The filing itself doesn't dilute, but it reserves the right to. Track subsequent 424B5 prospectus filings to see what was actually issued.
Frequently asked
What is the difference between a S-1 and a S-3?
S-1 (IPO Registration) and S-3 (Shelf Registration) are both SEC filings, but differ on audit status, deadline, length, and content scope. The table above lists every attribute that matters.
When should I read a S-1?
When researching an IPO or a follow-on offering from a smaller, less-established public company. The S-1 prospectus is your most complete look at the business before public-market reporting begins.
When should I read a S-3?
When a company you own files an S-3, especially a 'universal shelf' for ATM offerings. The filing itself doesn't dilute, but it reserves the right to. Track subsequent 424B5 prospectus filings to see what was actually issued.
See S-1 and a S-3 in real filings
Download any company's SEC filings as clean PDFs on FilingRadar — free, no signup.