When a company is about to sell new shares — whether through an IPO, a secondary offering, or an ongoing ATM program dripping shares into the market daily — they’re required to deliver a prospectus to buyers. The 424B family of SEC filings is how that prospectus gets publicly disclosed. Learning to read these filings is one of the highest-value skills an active investor can develop, because they often signal dilution events before the rest of the market has processed them.
The 424B Family: What Each Filing Type Means
The numbers and letters in 424B filings aren’t arbitrary — they reflect specific SEC rules governing when and how prospectuses must be filed. Here’s what each variant means in practice:
424B1: A prospectus filed under Rule 424(b)(1) — used when a final prospectus is filed that was omitted from or differs from the originally filed registration statement. Most common in IPO contexts. Seeing a 424B1 typically means an offering is pricing or has priced.
424B2: Filed under Rule 424(b)(2), this is a prospectus supplement relating to a shelf registration for a specific offering. Often seen with bank and institutional issuers’ structured note and MTN programs. Less common in the small-cap world.
424B3: This is the one to watch for active investors in small and mid-cap stocks. A 424B3 is a supplement to a previously filed base prospectus — and in the context of most small-cap companies, it almost always means an ATM (at-the-money) program is active and shares are being sold into the market. These filings appear daily or weekly for companies running ATM programs, and each one represents shares sold into the open market at prevailing prices.
424B4: The pricing supplement for a firm-commitment offering — the concrete pricing terms of an underwritten deal. A 424B4 means the offering has been priced at a specific number: X shares at $Y per share, for total gross proceeds of $Z. This is the filing that tells you exactly how much dilution just happened.
424B5: Similar to 424B4 but filed under a different rule — used for offerings off an existing shelf registration. When a company has a previously filed S-3 shelf and does a new offering against it, the pricing supplement is typically filed as a 424B5. This is the most urgent signal in the family: a concrete offering is happening right now, with specific terms, and the shares are about to hit the market.
How to Read a Prospectus Supplement
Whether it’s a 424B4 or 424B5, a pricing supplement for a concrete offering contains several key pieces of information:
- Offering price and shares: The exact per-share price and total shares being sold. This tells you immediately the discount to current market price.
- Use of proceeds: What the company says they’ll do with the money. “General corporate purposes and working capital” is generic cover; “fund our Phase 3 clinical trial for [drug]” is specific. Vague language about “working capital” often means the company needs the cash to survive, not to invest.
- Underwriter discounts: The fees paid to underwriters. Typical range is 5-8% for smaller deals, up to 10%+ for difficult placements. High underwriter discounts signal the deal was hard to place.
- Lock-up agreements: Whether insiders and existing shareholders are subject to lock-up periods preventing them from selling after the offering.
- Overallotment option: The “greenshoe” — whether underwriters have an option to sell additional shares (usually 15%) beyond the base offering size. If exercised, total dilution is larger than the headline number.
Why 424B Filings Move Faster Than Any Other Disclosure
An 8-K announcing a material agreement has to be filed within four business days of the triggering event. An insider transaction disclosed on Form 4 can take up to two business days. Quarterly earnings reports have multi-week post-period deadlines.
Prospectus supplements under Rule 424(b) must be filed by the second business day after pricing. In practice, most are filed same-day or the next morning. There’s also no four-day delay — the securities being sold are the deliverable, so the filing tracks the actual transaction in near real time.
This means that when a company prices an offering at 10 PM on a Tuesday, the 424B4 or 424B5 may be live on EDGAR before the market opens Wednesday. Investors who are monitoring EDGAR in real time have the information before most of the market has processed it. By the time a financial news service writes a headline about it, the early movers have already adjusted.
The 424B3 Drip: The Slow Dilution Most Investors Miss
While 424B4 and 424B5 filings announce discrete, visible events, the 424B3 filings from active ATM programs represent a different kind of dilution — slower, quieter, and often underappreciated.
An ATM program allows a company to sell shares continuously through a broker-dealer at prevailing market prices. Each sale requires a 424B3 supplement. A company running an active ATM might file ten or fifteen 424B3s in a single month, each one representing another batch of shares sold into the market. Individually, each filing looks minor. Cumulatively, they can represent 10-20% dilution in a quarter, all of it at prices that tracked the stock down as it fell.
DilutionWatch monitors the full 424B filing stream — not just the big discrete offerings, but the ongoing ATM drip and the specific terms of every prospectus supplement filed. When a 424B5 prices a $10M offering at a 15% discount to yesterday’s close, you should know about it in minutes, not hours. The filings are public; the question is whether you’re watching them.