Insider trades come from SEC Form 4 filings, and once you know the vocabulary they are easy to interpret. The single most important habit is to distinguish a genuine open-market decision from a mechanical event. Here is how.
Acquired vs. disposed
Every transaction is flagged as an acquisition (A), meaning shares coming in, or a disposition (D), meaning shares going out. This is the most reliable buy/sell indicator because it is set on every line, even for grants and exercises that do not carry a simple "buy" or "sell" label.
The transaction codes that matter most
- P: Open-market purchase. The insider bought shares with their own money. Generally the strongest bullish signal.
- S: Open-market sale. The insider sold shares. This is noisier, and can mean diversification, taxes, or a scheduled plan.
- M: Option exercise. The insider converted options into shares. Often paired with a sale, and different from a fresh cash purchase.
- A: Grant or award. Shares given as compensation rather than bought. Says little about conviction.
- F: Shares withheld for taxes. A mechanical disposition to cover tax on vesting, rather than a real sell decision.
10b5-1 plans are set up in advance
Many insider sales happen under a Rule 10b5-1 plan, a trading schedule set up in advance so the insider cannot be accused of acting on inside information. A sale flagged as 10b5-1 was decided months earlier and tells you little about the insider's current view. Our 10b5-1 filters let you separate these from discretionary trades.
Putting it together
The trades worth the most attention are discretionary open-market purchases (code P), especially several from different insiders at the same company in a short window. Routine grants, tax-withholding dispositions, and scheduled 10b5-1 sales are the background noise to filter out. When you browse an insider's history, read the code column first. It tells you whether a transaction is a decision or a formality.
Related: What is a Form 4? · What are cluster buys?