📄 SEC Education

424B Prospectus Supplements: The Most Important Filing Type You're Ignoring

The 424B family of SEC filings are prospectus supplements — documents that accompany or update an existing registration statement. They're filed when a company is actively selling securities. A 424B5 means an offering is executing right now. A 424B3 means an ATM program is drip-selling shares into the market daily.

Most retail investors never look at these filings. Institutional traders monitor them constantly. That's a large part of why institutions almost always get better prices.

The 424B Variants Decoded

• 424B1 — Preliminary prospectus, not final. Filed before pricing is set.
• 424B2 — Final prospectus for securities offered at a fixed price via a traditional underwritten offering. Less common for small-caps.
• 424B3 — Prospectus for securities sold on a "continuous" basis — most commonly used for ATM (at-the-market) programs. If you see multiple 424B3s for the same company over time, the ATM is active and shares are being sold regularly.
• 424B4 — Final prospectus for IPOs and large registered offerings. The "big event" filing.
• 424B5 — Prospectus supplement to an existing S-3 shelf. This is the most urgent signal: a concrete takedown from the shelf is happening now. The pricing, number of shares, and use of proceeds are all in this document.
• 424B7 — Combination of 424B3 and 424B5; used when an ATM program is being activated under an existing shelf.

What to Look for in a 424B5

When a 424B5 hits, read these sections immediately:

1. Cover page: Number of shares offered, offering price, gross proceeds. Calculate the discount to current market price.
2. Use of proceeds: "Working capital and general corporate purposes" = paying bills. "Repay outstanding indebtedness" = servicing debt or paying off toxic lenders.
3. Underwriting section: Who's the placement agent? H.C. Wainwright, Maxim Group, A.G.P. — these firms specialize in small-cap dilutive offerings.
4. Lock-up agreements: Are insiders locked up? If not, they may sell alongside the offering.
5. Dilution table: Usually shows net tangible book value before and after the offering, quantifying per-share dilution.

The 424B3 ATM Signal

A single 424B3 might just be a technical update to an ATM prospectus. But a pattern of 424B3 filings over weeks and months means the ATM is actively being used. The company is selling shares into the market continuously — no announcement, no deal closing, just persistent daily supply hitting the bid.

Check the frequency: monthly 424B3s suggest moderate ATM activity. Weekly or more frequently suggests aggressive selling. Compare to share count growth in the quarterly 10-Q to quantify how much was actually sold.