SEC Form 4 Transaction Codes Explained

Every SEC Form 4 filing carries a single-letter transaction code that tells you what actually happened - whether an insider bought shares with their own money, sold on a schedule, received a grant, or handed some stock back to cover taxes. It is the most important column on the form, and it is the difference between a real signal and pure noise.

Below is the complete list of Form 4 (and Form 5) transaction codes, in plain English, grouped the way the SEC groups them - with a note on whether each one is worth your attention as an investor.

The codes that matter most

Code	What it means	Signal
P	Open-market or private purchase. The insider bought shares. When it is at or near the current market price, this is the strongest bullish tell on the form - nobody is required to buy.	Strong
S	Open-market or private sale. The insider sold shares. Worth watching, but context matters - most selling is for liquidity or diversification, and much of it runs on pre-set 10b5-1 plans.	Watch
V	Voluntary early report. Marks a transaction reported before it was strictly required. A reporting note, not a transaction type of its own.	Noise

Compensation & tax codes (Rule 16b-3)

These cover pay packages and the mechanics around them. They are almost always about how an executive is compensated, not what they think of the stock.

Code	What it means	Signal
A	Grant, award, or other acquisition. The company gave the insider stock or units as compensation (RSUs, restricted stock). Not a conviction signal - they didn't pay for it.	Noise
M	Exercise or conversion of a derivative security. The insider turned previously granted options into shares. Common, and often followed by a sale (S) or tax withholding (F). Neutral on its own.	Noise
F	Shares withheld for taxes / exercise price. The company kept back shares to cover the tax bill (or option cost) when equity vested. Looks like a sale but is purely mechanical - the insider didn't choose to sell.	Noise
D	Disposition back to the issuer. Shares returned to the company (e.g. forfeiture or repurchase under a plan). Not a market transaction.	Noise
I	Discretionary transaction under a plan. A benefit-plan trade the insider elected (e.g. moving in/out of a company-stock fund). Rarely a meaningful signal.	Noise

Derivative security codes

These describe what happened to options, warrants, and other derivatives - not the underlying stock directly.

Code	What it means	Signal
C	Conversion of a derivative security into the underlying shares (e.g. a convertible note converting to stock).	Noise
X	Exercise of an in-the-money or at-the-money derivative. Exercising options that have value. Mechanical.	Noise
O	Exercise of an out-of-the-money derivative. Rare, since exercising a losing option is unusual - occasionally worth a look.	Watch
E	Expiration of a short derivative position. A written/short derivative lapsed.	Noise
H	Expiration or cancellation of a long derivative position with value received.	Noise

Gifts, wills & other codes

Code	What it means	Signal
G	Bona fide gift. Shares donated to charity or gifted to family. Not a market signal, though large gifts can carry tax or estate context.	Noise
L	Small acquisition under Rule 16a-6. A minor acquisition below the reporting threshold, reported for completeness.	Noise
W	Acquisition or disposition by will or the laws of descent and distribution (inheritance).	Noise
Z	Deposit into or withdrawal from a voting trust. An administrative transfer, not a buy or sell.	Noise
J	Other acquisition or disposition. A catch-all the SEC requires the filer to explain in a footnote - so read the footnote.	Read footnote
K	Transaction in an equity swap or similar instrument.	Noise
U	Disposition via tender of shares in a merger or change-of-control transaction. Tells you about a deal, not conviction.	Noise

Each code, explained

Here is what the most-searched Form 4 codes actually mean in practice, and whether each is worth acting on.

Form 4 Code P — Open-Market Purchase (Buy)

Code P means an insider bought shares on the open market with their own money, at or near the going price. Nobody is required to buy their own stock, so a P purchase is the single most bullish transaction on a Form 4 - especially from a CFO, or when several insiders file P buys within a few weeks. This is the only code InsiderTape treats as a core buy signal.

Form 4 Code S — Open-Market Sale

Code S means the insider sold shares on the open market. It is worth noting but rarely alarming on its own: executives sell for taxes, a house, or diversification, and a large share of selling runs on autopilot under pre-scheduled 10b5-1 plans. Check whether a sale was planned before reading conviction into it.

Form 4 Code A — Grant or Award

Code A is stock the company gave the insider as compensation - RSUs, restricted stock, or a similar award. The insider did not pay for it, so a code-A acquisition is not a buy signal, even though it raises their share count. Most "insider buying" headlines that look too good to be true are really grants.

Form 4 Code M — Option Exercise

Code M is the exercise or conversion of a derivative - the insider turned previously granted options into shares. It is a compensation mechanic, not a fresh vote of confidence, and it is often paired with a sale (S) or tax withholding (F). Treat a bare M as neutral. See real buys vs option exercises for the trap it creates.

Form 4 Code F — Shares Withheld for Taxes

Code F means shares were withheld to cover the taxes (or the exercise price) when an award vested. It appears as a disposition and can look like selling, but it is purely mechanical - the insider did not choose to sell; the company simply kept back enough shares to pay the tax bill. Ignore F for signal purposes.

Form 4 Code G — Gift

Code G is a bona fide gift of shares, typically to charity or family or for estate planning. No money changes hands at market, so it carries no buy or sell signal, though an unusually large gift can hint at tax or estate moves.

Form 4 Code C — Conversion of a Derivative

Code C is the conversion of a derivative security into common stock - for example a convertible note or preferred share converting to shares. It changes what the insider holds, but it is a mechanical event, not an open-market purchase.

Form 4 Code D — Disposition to the Issuer

Code D is a disposition back to the company - shares forfeited or repurchased under a plan rather than sold into the market. It tells you about plan mechanics, not conviction.

Why the code changes everything

The most common mistake investors make with insider data is treating every transaction as equal. A director exercising decade-old options and having shares withheld for tax (codes M and F) tells you nothing. A CFO filing a code-P open-market purchase the week after a rough earnings call is a completely different story. Same form, opposite meaning - and the only thing separating them is that one letter.

For the full anatomy of the filing, see how to read an SEC Form 4. For the trap where a below-market "buy" is really an option exercise, see real insider buys vs option exercises.