SEC Form 4 is one of the most powerful — and least understood — public documents in the US financial system. It's free. It's public. It's filed within 48 hours of every insider transaction. And most retail investors have never looked at one.
What Is Form 4?
Form 4 is a disclosure document filed with the US Securities and Exchange Commission under Section 16(a) of the Securities Exchange Act of 1934. It must be filed by any corporate insider — defined as an officer, director, or beneficial owner of more than 10% of a company's equity securities — within two business days of any transaction involving that company's stock.
The filing captures the who, what, when, and how much of every insider trade. It's publicly available on the SEC's EDGAR database the moment it's accepted — usually within hours of filing.
Who Has to File Form 4?
- Chief Executive Officers (CEOs)
- Chief Financial Officers (CFOs) and other C-suite officers
- Board of Directors members
- Shareholders owning more than 10% of any class of equity securities
Why Does This Matter to You?
When a CEO buys $2 million of their own company's stock in the open market, they're making a statement. They know the product roadmap. They know the next earnings report is coming. They know what deals are in the pipeline. And they decided — with their own money, at market price — that the stock is worth buying right now.
Academic research published in the Journal of Financial Economics has consistently shown that clusters of insider buying — particularly by high-ranking officers making large open-market purchases — tend to precede positive stock returns over 6-12 month horizons. This is not a secret. Hedge fund compliance desks monitor Form 4 filings daily. Now you can too.
The Signal vs. The Noise
Not all Form 4 transactions are created equal. The one you care about is transaction code P — open-market purchase. Everything else is largely noise:
- A (Award) — shares granted as compensation. The insider paid nothing. Zero signal.
- M (Option Exercise) — converting options to shares. Usually followed immediately by a sale. Neutral to slightly negative.
- F (Tax Withholding) — automatic. Not a decision. Ignore it.
- S (Sale) — worth noting, but context matters enormously. Insiders sell for many reasons unrelated to their view of the stock.
The bottom line:
An insider buy (code P) is a deliberate, voluntary decision to spend personal cash at whatever the market is offering. An insider sell could mean anything. Focus your attention accordingly.
InsiderRadar surfaces Form 4 data directly from SEC EDGAR in real time. Search any US stock ticker to see the latest insider transactions — or check the unusual activity feed for the largest open-market purchases across all companies in the last 30 days.