Form 4 Transaction Codes Explained (P, S, M, A, F, G)
Every transaction an insider reports on an SEC Form 4 carries a one-letter transaction code. The most important one is P — an open-market purchase, where an insider chose to buy their own company’s stock at the market price with their own money. The rest range from ordinary sales to automatic, compensation-driven events that say little about what an insider actually believes. Here’s what each code means, and how to tell a real decision from routine noise.
Form 4 data is public and free on the SEC’s EDGAR system. Reading it is legal and ordinary — these are after-the-fact disclosures, not tips. This article is informational and not financial advice.
First, what is a Form 4?
When a corporate insider — a director, an officer, or a shareholder who owns more than 10% of a company — buys or sells that company’s stock, U.S. law requires them to report it to the SEC on a Form 4, usually within two business days of the trade. It’s one of the few mandatory, public windows into what the people closest to a company are doing with their own money. (For the bigger picture, see Is insider buying a good sign?)
The codes that matter most
| Code | What it means | Plain English |
|---|---|---|
| P | Open-market or private purchase | The insider bought shares at market — a deliberate use of their own cash. |
| S | Open-market or private sale | The insider sold shares. |
| A | Grant, award, or other acquisition | Shares given to the insider (e.g. equity compensation) — not bought. |
| M | Exercise or conversion of a derivative (e.g. options) | Turning options/units into shares — a comp/vesting event, not a fresh bet. |
| F | Shares withheld to pay tax or an exercise price | Mechanical: shares handed back to cover taxes, not a market decision. |
| G | Bona-fide gift | Shares given away — no economic purchase. |
There are more (C, D, E, H, I, J, K, L, O, U, V, W, X, Z) covering conversions, expirations, swaps, tender offers, estate transfers and edge cases. The full, authoritative list lives on the SEC’s own reference page (linked below). But for reading insider activity, the six above carry almost all the meaning.
Signal vs. noise: which codes reflect a real decision
Not every Form 4 line is equally informative. A useful way to read them — this is analytical convention among investors, not an official SEC ranking — is to separate intentional, open-market decisions from routine, compensation-driven events:
- Intentional (a real decision): P (open-market purchase) above all, and S (open-market sale). The insider actively chose to commit cash or to sell into the market.
- Routine / mechanical (mostly noise): A (granted shares), M (option exercise), F (tax withholding), G (gifts). These follow comp plans, vesting schedules, and tax mechanics — they happen more or less automatically and don’t reflect a fresh view on the stock.
This is exactly why a feed that lumps all Form 4 activity together can be misleading: a wave of A and M codes is just payday, not conviction.
Why “P” gets the most attention
An open-market purchase is the cleanest of the codes for one simple reason: there is usually only one motive behind it. An insider sells for many ordinary reasons — taxes, diversifying a concentrated position, a house, a pre-scheduled plan. But an insider generally buys their own stock for just one: they think it’s worth more than the price. They’re putting personal, after-tax money at risk on that view.
That’s the idea behind “intentional” buys — and it’s why DirectorScope defaults to showing open-market purchases (code P) and de-emphasizes the comp/automatic codes. It’s a cleaner read on what insiders are choosing to do. (Worth knowing the limits, too — see Is insider buying a good sign?.)
FAQ
What does “P” mean on a Form 4? A P is an open-market (or private) purchase — the insider bought shares at the market price with their own money. It’s widely viewed as the most informative single code.
What’s the difference between P and A? P is a purchase the insider chose to make and paid for. A is an acquisition by grant or award — shares the company gave them (typically as compensation). One is a bet; the other is payday.
Is an option exercise (code M) a bullish signal? Usually not on its own. M reflects exercising or converting options/units that vested under a comp plan — a scheduled event, not a fresh market decision. Watch what the insider does with the resulting shares (hold vs. sell) for more meaning.
What does S mean — should I worry about insider selling? S is an open-market sale. Sales are noisier than purchases because insiders sell for many benign reasons (liquidity, taxes, diversification, pre-scheduled plans). A single sale rarely says much; patterns and context matter more.
How quickly must an insider file a Form 4? Before the end of the second business day following the transaction.
Source: SEC EDGAR — Ownership Reports & Transaction Codes. DirectorScope turns these public SEC filings into a clean view of intentional insider buying. Informational only — not financial advice.