Most reverse-split trades that go badly fail for the same reason: somewhere in the EDGAR feed, a 424B prospectus supplement was filed, and the trader didn't notice. By the time the price action started moving, the company was already selling new shares directly into the rally.
This is the single most preventable mistake in reverse-split trading. Here's what a 424B actually is, why it's so dangerous, and how to check for one before every trade.
The hierarchy: S-3 → 424B
To understand the 424B, you need to understand the filing it's supplementing.
An S-3 registration statement is the document a company files with the SEC saying, in effect, "we may want to sell up to [X] new shares over the next few years." It's a permission slip. It doesn't actually sell anything. It just gets approval to sell, on the company's timeline.
That permission slip is called a shelf registration, because the shares sit on the shelf, ready to be deployed whenever the company chooses. Most public companies have an S-3 on file. By itself, an S-3 isn't necessarily a red flag.
The 424B filing is the moment the company actually pulls shares off the shelf and sells them. The 424B is the prospectus supplement that says, "we are now selling [Y] shares at [price] under our previously registered shelf." This isn't a may. It's an is.
Why this destroys a reverse-split trade
The whole structural setup of a tradeable reverse split depends on supply being constrained. The tight post-split float is what makes the price move on normal buying pressure.
A 424B filing detonates that constraint. The company is creating new supply on demand, and selling it into exactly the rally retail traders are trying to catch. Every share you buy could be a share the company just sold to your broker. The float you calculated this morning was wrong by the close.
A 424B in the same filing window as a reverse split is the company telling you, in writing, that they intend to dump shares into the rally. Believe them.
The variants you'll see
Several 424B subtypes exist. The most common:
- 424B1 — prospectus for a public offering
- 424B2 — prospectus supplement with pricing information
- 424B3 — supplement containing material changes or new information
- 424B4 — pricing for a previously announced offering
- 424B5 — prospectus supplement (common for ATM activity)
You don't need to memorize the subtypes. For trading purposes, any 424B filed in the same window as a reverse split announcement is a red flag — full stop. Walk away.
How to check, every single time
On the company's EDGAR page:
- Click Filings
- In the "Filing type" box, type
424and press enter - Look at the most recent filing date
If the most recent 424B is more than 12 months old, the shelf is probably dormant. If it's in the last 30 days — or worse, the last 7 days — the company is actively selling.
Cross-check with the company's most recent S-3. The S-3 will tell you the total capacity of the shelf. If the S-3 authorizes $200 million worth of new shares and the 424B filings show only $30 million sold so far, there's $170 million of dilution ammunition still waiting to be deployed.
The ATM offering — special case
An at-the-market (ATM) offering is a particularly aggressive variant: instead of pricing the offering once and selling all the shares at that price, the company drips shares directly into the open market at whatever price it's trading at on any given day.
ATM offerings are disclosed in 424B filings (usually 424B5) and in the S-3 itself under a section called "Plan of Distribution" or "ATM Offering Agreement." If you see those words: the company is selling into every rally, by design. That's a setup that breaks the math.
The honest takeaway
You don't need to be an SEC lawyer. You just need to do this one check every time:
- Is there a 424B filed in the last 30 days? → walk away
- Is there active ATM language in the S-3? → walk away
- Is the most recent 424B more than 12 months old? → keep researching
- Is there no S-3 on file at all? → cleanest possible setup
Three minutes of checking on EDGAR. The trades you skip because of this filter will save you ten times more money than the trades you take because of any other filter we teach.
We built the SEC Filing Checklist specifically to walk through this exact check with green/red flag callouts under the S-1/S-3 section. Use it on the next reverse split that catches your eye.