If you follow insider trading data at all, everything you see traces back to one document: SEC Form 4, Statement of Changes in Beneficial Ownership. It is short, it is public, and it is filed tens of thousands of times a year.
It is also widely misread. This guide covers what is actually in it.
Who files one
Section 16 of the Securities Exchange Act of 1934 defines a class of people as insiders:
- Officers — the CEO, CFO, and other policy-making executives
- Directors — anyone on the board
- 10% owners — anyone who beneficially owns more than 10% of a registered class of the company's equity
When any of them trades their own company's stock, they must report it.
How fast
Two business days from the transaction date. That deadline came in with the Sarbanes-Oxley Act in 2002. Before that, insiders could wait until the tenth day of the following month — which meant a purchase made on 1 March might not surface until 10 April.
Two things follow from the modern deadline:
- The transaction date and the filing date are different, and it is the transaction date that matters. A filing that lands on Thursday may describe a trade made on Tuesday.
- Filings cluster. Most Form 4s are submitted late in the trading day, and the heaviest volume is between 4pm and 6pm Eastern.
What is on the form
A Form 4 has two tables, and the distinction between them is the single most important thing to understand.
Table I — Non-Derivative Securities. The common stock itself. When an insider buys or sells shares, it appears here.
Table II — Derivative Securities. Options, warrants, restricted stock units, convertible notes. Grants of stock options appear here, as do exercises.
Both tables report, per row:
- the transaction date
- a transaction code — one letter describing what happened
- the number of shares
- the price per share
- whether the securities were acquired (A) or disposed of (D)
- how many shares the insider held afterwards
The transaction code is everything
This is where most people go wrong. It is tempting to treat every "acquired" row as insider buying. It is not.
| Code | What it means | Is it buying? |
|---|---|---|
| P | Open-market or private purchase | Yes |
| S | Open-market or private sale | It is selling |
| A | Grant or award under an equity plan | No — this is pay |
| M | Exercise or conversion of a derivative | No — no market purchase happened |
| F | Shares withheld to pay tax or an exercise price | No — a disposal, but not a decision to sell |
| G | Bona fide gift | No money changed hands |
An A is the company handing an executive shares as compensation. They did not choose to buy and they paid nothing.
An M is an executive converting options granted years ago into shares. It shows up as an acquisition, but no purchase happened at the market price — and it is very frequently paired with a same-day S sale of the resulting shares.
An F is shares handed straight back to the company to cover the tax bill on a vesting award. Mechanically a disposal, but nobody decided to sell anything.
Only P means somebody looked at the market price and decided to spend their own money.
See every transaction code and how we classify it →
Footnotes carry real information
Form 4 footnotes are free text, and filers use them to explain things the structured fields cannot hold. Two are worth always reading:
- Weighted average prices. When a trade filled across many prices during the day, the filer reports a single weighted average in the price column and explains the actual range in a footnote. The reported price is a summary, not the price of any individual fill.
- Rule 10b5-1 plans. Filings before March 2023 have no machine-readable field for this, so the only evidence a trade was pre-scheduled is a sentence in the footnotes.
Amendments happen
Insiders make mistakes and correct them with a Form 4/A. An amendment restates an earlier filing — a wrong date, a wrong share count, a missing transaction.
This means insider trading data is not immutable. A trade you saw last week can change value or disappear entirely. That is not a data problem; it is the public record being corrected.
Awkwardly, the SEC's XML does not include the accession number of the filing being amended, so linking an amendment to its original has to be inferred from the issuer, the reporting period, and the reporting owner.
Where to read them
Every Form 4 is free and public on SEC EDGAR. The raw filings are XML, and the SEC provides a human-readable rendering of each one.
Everything on this site is parsed from those filings within minutes of publication, and every row links back to the original document. If a number here disagrees with the filing, the filing is right.
What Form 4 does not tell you
- Why. There is no field for motive. An insider selling might be buying a house, paying a tax bill, diversifying, or getting out.
- What they think of the price. A grant is priced at whatever the plan says. An exercise is priced at the strike set years ago. Only an open-market purchase happens at a price the insider chose to accept.
- Anything about non-insiders. Form 4 covers Section 16 insiders only. A large shareholder at 9.9% files nothing.
Start with what insiders are actually buying, then read whether insider buying is a useful signal.