Transaction codes
Every Form 4 line carries a one-letter code, and the entire meaning of a filing rests on it. Two of the letters are real trades; the rest are compensation mechanics, transfers and bookkeeping that happen to move shares. New to the form itself? Start with what a Form 4 is and how to read one.
Real buys and sells — the signal
| Code | Meaning | Reading it |
|---|---|---|
| P | Bought shares with their own money | The strongest signal on the form: the insider chose to spend their own cash on the stock. Usually read as confidence. |
| S | Sold shares | Insiders sell for many ordinary reasons — taxes, a house, spreading their savings around — so a sale means much less than a buy. Check the 10b5-1 flag: if it’s set, the sale ran on an automatic schedule set up months earlier, not a decision made that day. |
Pay-package mechanics — mostly noise
| Code | Meaning | Reading it |
|---|---|---|
| A | Received shares from the company as pay | Stock compensation arriving on schedule. The insider didn’t decide to buy anything. |
| M | Turned stock options into shares | An option is a right to buy shares at a preset price; this code means one was cashed in for actual shares. Often paired with a same-day sale (S) of those shares. |
| F | Shares kept back to cover taxes | When stock pay becomes fully owned (“vests”), the company keeps some of the shares to pay the tax bill. It looks like a sale in the table, but the insider never chose to sell. |
| X | Cashed in a profitable stock option | Same idea as M: an option converted into shares, here one whose preset price is below the current share price (“in the money”). |
| D | Gave shares back to the company | Shares returned to the company that issued them, usually to settle some arrangement. |
| I | A trade made inside a benefit plan | A broker or plan administrator moved the shares under a company benefit plan. The insider set the plan’s rules earlier but didn’t place this trade. |
Gifts, inheritance, and transfers
| Code | Meaning | Reading it |
|---|---|---|
| G | Gave shares away as a gift | No money changed hands — the shares went to a charity, a family trust, or a relative. Never a sale, whatever the row looks like. |
| C | Swapped one type of security for another | One kind of holding became another — for example, preferred shares turning into ordinary shares. The overall stake barely changes. |
| W | Inherited, or passed on through a will | Shares changing hands because someone died, not because anyone traded. |
| Z | Moved shares in or out of a voting trust | A voting trust holds shares so someone else can vote them. This is a change of who holds the shares, not a buy or a sell. |
Everything else
| Code | Meaning | Reading it |
|---|---|---|
| J | Something else — see the footnotes | The catch-all code. What actually happened is spelled out in the filing’s footnotes. |
| K | A swap contract | A side contract that changes how much the insider gains or loses from the stock, without any shares actually trading. |
| L | A small purchase | A minor buy allowed under a special SEC rule (16a-6). Too small to read anything into. |
| U | Handed shares over in a buyout | The insider turned in their shares during a merger or takeover, along with other shareholders. |
| E | A contract the insider had sold expired | A derivative the insider had written (sold to someone else) reached its end date. No shares traded. |
| H | An option expired unused | The insider let an option lapse without cashing it in — usually because it had become worthless. No shares moved. |
| O | Cashed in an unprofitable stock option | Exercising an option even though its preset price was above the market price. Rare, and usually tied to a corporate event rather than a normal choice. |
Common questions
Which Form 4 transaction codes are actual trades?
Only P (the insider bought shares) and S (the insider sold shares), and only when the line carries a real price. Every other code reports pay-package events, gifts, transfers or bookkeeping that happen to move shares.
What does code A mean on a Form 4?
The company gave the insider shares as part of their pay, arriving on a set schedule. It is not a decision by the insider to buy stock.
What does code F mean on a Form 4?
When stock pay becomes fully owned (“vests”), the company keeps back some of the shares to cover the tax bill. It looks like a sale in the table, but the insider never placed a sell order.
What does code M followed by code S mean?
The insider turned stock options into shares (M) and sold those shares (S), often the same day — the standard way executives cash out stock pay. It reads very differently from an insider choosing to buy shares with their own money.
Keep reading
- What is SEC Form 4? — SEC Form 4 explained: who must file it, the two-business-day deadline, what Tables I and II report, and how insider buys and sales become public record.
- How to read a Form 4 — A walkthrough of a Form 4 insider filing: the relationship boxes, every Table I and Table II column, the footnotes, and the Rule 10b5-1 checkbox.
- Form 4 filing deadlines — When a Form 4 is due: the two-business-day rule from Sarbanes-Oxley, EDGAR’s 10 pm cutoff, the narrow exceptions, and what actually happens to late filers.
- Form 3 vs Form 4 vs Form 5 — The three Section 16 ownership forms compared: Form 3 when you become an insider, Form 4 within two business days of a trade, Form 5 as the annual catch-up.
- Rule 10b5-1 trading plans — What a Rule 10b5-1 trading plan is, the 2023 cooling-off and disclosure amendments, the Form 4 checkbox, and how to read planned versus discretionary trades.
- What is insider trading? — Insider trading is legal when insiders report their trades and illegal when anyone trades on material non-public information.
- Reading insider buying — Which insider-buying patterns carry information according to the published research — cluster buys, purchase size versus stake, the buyer’s role — and which are noise.