Form 4 Transaction Codes: The Complete Reference

Every line on an SEC Form 4 carries a one- or two-letter transaction code in the column labelled "Code." That code is the difference between an insider spending their own money on stock and the company handing them shares as pay. Read it wrong and you will mistake a payroll event for a conviction buy.

Most guides cover four or five codes. This page covers all of them, grouped the way the SEC's own Form 4 instructions group them, with a note on what each one is worth as a signal. If you are new to the filing itself, start with how to read a Form 4 and come back here as a lookup table.

The short version

If you only remember one thing: P is the code that matters.

Code	Meaning	Signal value
P	Open-market or private purchase	High — the insider chose to buy
S	Open-market or private sale	Low to moderate — many innocent reasons
A	Grant or award	None — compensation, not a decision
M	Exercise/conversion of a derivative	None — compensation mechanics
F	Shares withheld to pay taxes	None — automatic
G	Bona fide gift	None

Everything below is the full picture.

General transaction codes

These are the ordinary open-market trades — the ones that carry real information.

P — Open-market or private purchase of a non-derivative or derivative security. The signal. The insider bought shares at the prevailing market price with their own after-tax money. Nobody required it, and it is publicly accountable. This is the only code this site counts as insider buying, and it is the basis of every cluster buy we publish.

S — Open-market or private sale. A discretionary sale. Genuinely informative sometimes, but heavily diluted by tax bills, diversification, house purchases and divorce settlements. See insider buying vs. insider selling for why buys are the cleaner side of the ledger.

V — Transaction voluntarily reported earlier than required. Not a transaction type in its own right — a marker that the insider filed ahead of the deadline. Read the accompanying code for the substance.

Rule 16b-3 transactions (compensation mechanics)

These are transactions between the insider and the company itself, exempted from short-swing profit rules. Almost none of them reflect an opinion about the stock.

A — Grant, award or other acquisition under Rule 16b-3(d). The board granted shares or units. The insider acquired stock without buying it. Headlines that describe this as "insider buying" are simply wrong.

D — Disposition to the issuer under Rule 16b-3(e). Shares returned to the company, e.g. a repurchase or forfeiture.

F — Payment of exercise price or tax liability by delivering or withholding securities. When equity vests, the company keeps back enough shares to cover the tax bill. It appears as a disposition, and it means nothing. This is the single most common cause of "the CEO just dumped stock!" panic on social media.

I — Discretionary transaction under Rule 16b-3(f). A volitional move inside a company benefit plan — for example switching a 401(k) balance into or out of company stock. Mildly informative at best; it is usually a plan-administration event.

M — Exercise or conversion of a derivative security exempted under Rule 16b-3. Options or RSUs becoming actual shares. Routine. Frequently followed immediately by F or S to cover taxes, which is where the misreading starts.

Derivative security codes

Options, warrants and convertibles, where the transaction is not exempt under 16b-3.

C — Conversion of a derivative security. Mechanical.

E — Expiration of a short derivative position. Housekeeping.

H — Expiration or cancellation of a long derivative position with value received. Housekeeping.

O — Exercise of an out-of-the-money derivative security. Unusual and occasionally interesting: exercising an option that is underwater is a strange thing to do unless the holder expects the shares to recover. Rare enough that it is worth reading the footnotes.

X — Exercise of an in-the-money or at-the-money derivative security. Ordinary. The insider is capturing existing value, not making a new bet.

Exempt transactions and small acquisitions

G — Bona fide gift. Shares to family, a trust or a charity. No investment content — though large gifts are sometimes read as estate-planning signals.

L — Small acquisition under Rule 16a-6. An acquisition small enough to fall below the reporting thresholds that would otherwise apply.

W — Acquisition or disposition by will or the laws of descent and distribution. Inheritance.

Z — Deposit into or withdrawal from a voting trust. Structural.

Other codes

J — Other acquisition or disposition. A catch-all. The SEC requires a footnote explaining it, so if you see a J, read the footnote — this is the one code where the explanation is the whole content.

K — Transaction in an equity swap or similar instrument. Derivative exposure rather than share ownership. Worth noting when it is large, because it can change an insider's economic exposure without changing their share count.

U — Disposition pursuant to a tender of shares in a change-of-control transaction. The insider tendered into a takeover. A deal event, not a view.

The 10b5-1 checkbox

The code is not the whole story. Form 4 also carries a checkbox indicating that a transaction was made under a Rule 10b5-1(c) trading plan — a schedule the insider set up in advance. A code-P purchase executed automatically by a plan adopted six months ago tells you much less than one an insider decided to make last week.

Always read the code and the checkbox together. We cover the distinction in detail in what 10b5-1 plans do to an insider buying signal.

Using this at scale

Reading codes correctly on one filing is the skill. The edge is applying it to thousands: filtering everything down to code P, discarding the compensation noise, and watching for the moments when several insiders buy the same company at once.

That is what the cluster-buy screener does — it counts only open-market purchases, which is why its numbers are so much smaller, and so much more interesting, than a raw "insider activity" feed. Our methodology page sets out the filters in full.

Frequently asked questions

Which Form 4 code means an insider actually bought stock? Code P — an open-market or private purchase. Code A is a grant and code M is an option exercise; neither involves the insider buying shares at market price.

Why does a Form 4 show a huge sale right after an option exercise? That is the M → F/S sequence: the option converts to shares, then shares are withheld or sold to cover the exercise price and the tax bill. It is mechanical and carries essentially no information about the insider's view.

What does code F mean on a Form 4? Shares surrendered to the company to pay an exercise price or tax liability when equity vests. It is a disposition on paper, but the insider did not choose to sell into the market.

Is a code J transaction important? It can be — J is "other," and the SEC requires a footnote explaining it. The footnote, not the code, tells you what happened.