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Form 4 Transaction Codes: The Complete List Explained

Chad Hartman

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Published July 7, 2026 · Last updated July 7, 2026

Every SEC Form 4 filing carries a single letter in Column 4 that determines whether the transaction it reports means anything at all. Financial news headlines rarely mention it. A share count and a name are enough to generate a story — "CEO Sells 200,000 Shares" — regardless of whether that sale was a discretionary market call or an automatic tax withholding triggered by an RSU vesting. The SEC defines exactly twenty of these codes, split across five categories in the form's own instructions. The difference between them is the difference between an insider making an economic decision and an insider going through a scheduled, mechanical process. This is the complete reference: every code, what it actually means, and how much analytical weight it deserves.

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Table of Contents

Quick Reference: All 20 Codes at a Glance

The SEC's Form 4 instructions group every transaction code into five categories: General Transaction Codes, Rule 16b-3 Transaction Codes, Derivative Securities Codes, Other Section 16(b)-Exempt and Small Acquisition Codes, and Other Transaction Codes. The table below lists all twenty in that order, with the signal weight each one carries for fundamental and insider-activity research.

Code Category Meaning Signal Weight
P General Open-market or private purchase High — a voluntary, out-of-pocket capital decision
S General Open-market or private sale Conditional — depends on size, footnotes, and 10b5-1 status
V General Transaction voluntarily reported earlier than required None — a reporting-timing flag, not a transaction type
A Rule 16b-3 Grant, award, or other acquisition under a compensation plan None — compensation delivery, not a market decision
D Rule 16b-3 Disposition of shares back to the issuer None — typically forfeiture or a plan-based return
F Rule 16b-3 Shares withheld to cover exercise price or tax on vesting None — automatic tax withholding, not a sale decision
I Rule 16b-3 Discretionary transaction under a Rule 16b-3(f) plan Low — plan-governed, with limited insider discretion
M Rule 16b-3 Exercise or conversion of a derivative security Conditional — check for a same-day disposition
C Derivative Conversion of a derivative security None — mechanical exercise of an existing right
E Derivative Expiration of a short derivative position None — a written option lapsed unexercised
H Derivative Expiration or cancellation of a long derivative position with value received Low — passive settlement, not a market call
O Derivative Exercise of an out-of-the-money derivative security Low — often plan-timed or forced by expiration
X Derivative Exercise of an in-the-money or at-the-money derivative security Conditional — check whether the shares were retained or sold
G Other Exempt Bona fide gift None — no market view expressed
L Other Exempt Small acquisition exempt under Rule 16a-6 None — a de minimis acquisition below the reporting threshold
W Other Exempt Acquisition or disposition by will or the laws of descent and distribution None — an estate event, not a trading decision
Z Other Exempt Deposit into or withdrawal from a voting trust None — a governance structure change, not a market transaction
J Other Other acquisition or disposition (described in a footnote) Depends entirely on the footnote
K Other Equity swap or instrument with similar characteristics Modifier — appended to another code, not a standalone transaction
U Other Disposition pursuant to a tender of shares in a change-of-control transaction None — forced by the acquiring party's tender terms

General Transaction Codes: P, S, V

These are the only codes that can, on their own, represent a voluntary market decision.

P — Open-market or private purchase. The insider spent personal capital to buy shares or a derivative security. No plan required it, no vesting schedule delivered it. Of all twenty codes, P is the one that most directly reflects what an insider believes about the stock right now.

S — Open-market or private sale. The insider sold shares or a derivative security at the current price. It is a voluntary act by definition, but S is common enough — executives routinely diversify concentrated equity positions — that the raw code alone says little. Whether an S transaction carries weight depends on context the code itself doesn't supply: size relative to total holdings, a 10b5-1 footnote, and whether the filing breaks an established pattern.

V — Transaction voluntarily reported earlier than required. This is not a transaction type; it is a timing flag. Certain small transactions qualify for deferred reporting on Form 5, and a reporting person can choose to disclose one early on a Form 4 instead. When V appears, look at the actual code it accompanies to understand the underlying event.

Rule 16b-3 Transaction Codes: A, D, F, I, M

These five codes cover more Form 4 filings than any other category, because most executive compensation today isn't cash — it's equity. Rule 16b-3 exempts these compensation-related transactions from Section 16(b) short-swing profit liability, and the codes here cover the mechanics: grants, forfeitures, tax withholding, plan-based dispositions, and derivative exercises.

A — Grant, award, or other acquisition pursuant to Rule 16b-3(d). An RSU grant, an option award, or any other equity compensation delivered under the company's plan. The compensation committee made this decision, not the insider. A large A transaction is the single most common reason a Form 4 shows a big share count with zero investment signal.

D — Disposition to the issuer pursuant to Rule 16b-3(e). Shares surrendered back to the company — most often unvested RSUs forfeited on departure, or shares returned under a specific plan provision. This reduces share count but reflects an employment event, not a market view.

F — Payment of exercise price or tax liability by delivering or withholding securities. When equity compensation vests or an option is exercised, the recipient owes tax. Rather than writing a check, the company withholds a portion of the shares automatically. F transactions generate a large share of what financial media casually labels "insider selling" — no cash was ever received in the traditional sense, and no discretionary decision to sell was made.

I — Discretionary transaction under Rule 16b-3(f). A transaction inside a tax-conditioned plan — commonly a 401(k) company stock fund — where the insider elects to move money in or out of company stock. It carries limited discretion, but the plan structure and required cooling-off periods between opposite-direction elections constrain how much any single I transaction reveals.

M — Exercise or conversion of a derivative security exempted under Rule 16b-3. The mechanical act of exercising options is not itself informative — options get exercised when they're in the money and approaching expiration regardless of the holder's outlook. What matters is what happens next. An M followed immediately by an S on the same or following business day is an exercise-and-sell: cash generated, no equity conviction retained. An M with no corresponding sale means the insider kept the shares — a meaningfully different signal from the same exercise event.

Derivative Securities Codes: C, E, H, O, X

None of the five codes in this category represent a trading decision on their own — they're the mechanical vocabulary for options, warrants, and convertible instruments in Table II, covering transactions the Rule 16b-3 codes above don't reach.

C — Conversion of a derivative security. A convertible instrument — often preferred stock or a convertible note — converts into the underlying common equity per its predefined terms. This is contractual mechanics, not a market decision.

E — Expiration of a short derivative position. A written (short) option position expires unexercised. The insider who wrote the option collected the premium and the obligation simply lapsed — not itself a directional signal.

H — Expiration or cancellation of a long derivative position with value received. A held derivative position expires or is cancelled, and the holder receives some value in the process — commonly cash settlement in a merger or a corporate action affecting outstanding options. It is a passive event driven by a corporate transaction, not a trading decision.

O — Exercise of an out-of-the-money derivative security. The insider exercises an option or right at a strike price above the current market value for a call, or below it for a put. This usually happens for structural reasons — a plan requiring exercise before expiration — rather than because the position suddenly became attractive.

X — Exercise of an in-the-money or at-the-money derivative security. The more common exercise scenario: the option is profitable to exercise at current prices. As with code M, the exercise itself is close to automatic once an option is deep in the money. The signal lives in whether the resulting shares were sold immediately or retained.

Other Exempt and Small Acquisition Codes: G, L, W, Z

The four codes here have nothing to do with compensation or trading at all — they cover what happens to shares during a gift, a death, a small transfer, or a change in who controls the vote.

G — Bona fide gift. Shares transferred to family members, a foundation, or another recipient with no cash changing hands. A G transaction expresses no view on the stock — the insider is not selling and is not signaling anything bearish by giving shares away.

L — Small acquisition exempt under Rule 16a-6. The SEC exempts acquisitions that, combined with other acquisitions of the same class over the prior six months, don't exceed $10,000 in market value — provided the insider doesn't dispose of any of it within that same six-month window. These are minor transactions by design; the dollar threshold itself is the reason they carry no analytical weight.

W — Acquisition or disposition by will or the laws of descent and distribution. An inheritance event. Shares change hands because of a death, not a market decision by anyone currently holding them.

Z — Deposit into or withdrawal from a voting trust. Shares move into or out of a voting trust structure — a governance arrangement, not a change in the beneficial owner's economic position or market outlook.

Other Transaction Codes: J, K, U

The final three codes are the odd ones out: a catch-all for anything the other categories don't capture, a modifier for equity swaps, and a forced disposition during a change-of-control deal.

J — Other acquisition or disposition. The SEC's catch-all. When no other code fits, the filer uses J and is required to describe the actual nature of the transaction in a footnote. A J transaction's meaning is entirely dependent on that footnote — never treat a bare J as informative on its own; always read what it's attached to.

K — Transaction in an equity swap or instrument with similar characteristics. K is not a standalone transaction type. The form's own instructions specify it should be appended alongside the code that actually describes the transaction — for example, "S/K" for a sale executed through an equity swap. Seeing K by itself in a summary or a screener output usually means the underlying code was truncated somewhere in the data pipeline.

U — Disposition pursuant to a tender of shares in a change-of-control transaction. Shares tendered into an acquirer's tender offer during a merger or acquisition. This is forced by the terms of the deal, not a discretionary decision by the insider — everyone tendering shares under the same offer gets the same code regardless of their personal view of the transaction.

How Codes Combine: Modifiers and Amendment Flags

Two codes function differently from the eighteen that describe standalone transactions. K, as covered above, is a modifier appended to another code rather than a transaction type on its own — it signals that an equity swap or similar derivative structure was involved in executing the reported transaction. V works similarly as a timing flag rather than a transaction description, marking that a transaction eligible for deferred Form 5 reporting was disclosed early on a Form 4 instead.

A separate set of designators — the numbers 3, 4, and 5 — can appear next to a transaction code to flag a correction rather than describe the transaction itself. When a transaction that should have been reported on a prior Form 3 is instead being disclosed now, the filer places a "3" in the code column. A transaction that should have appeared on an earlier Form 4 gets a "4" appended to its code — an open-market purchase reported late shows as "P4." A transaction eligible for Form 5 that's being reported now gets a "5." None of these designators change what the underlying code means; they flag that the disclosure itself is catching up on something that should have appeared earlier.

Reading the Code Column for Signal, Not Just Definition

Twenty codes exist because the SEC needs to categorize every possible way beneficial ownership can change hands. Compensation, estate transfers, governance structures, derivative mechanics, and voluntary market activity all have to fit somewhere. But for an investor trying to extract a signal from insider activity, most of that categorization exists to rule things out. Of the twenty, only P carries unconditional weight. S, M, and X carry conditional weight that depends on context the code itself doesn't provide — size, footnotes, and what transaction happened immediately before or after. The remaining sixteen codes almost never represent a market view: they're compensation delivery, tax mechanics, estate events, gifts, or corporate actions that happen to an insider rather than being chosen by one.

This is why a share count in a headline is close to meaningless without the code attached to it. A $4 million insider "sale" reported as code F is a company withholding shares for taxes on a scheduled RSU vesting. The same dollar figure reported as code S with no 10b5-1 footnote is a discretionary decision to convert equity into cash. Same number, same direction, entirely different meaning — and the transaction code is the only field on the form that tells them apart.

The GeminIQ Edge: Codes Without the Memorization

A standard news feed reports the share count and the dollar total. It rarely surfaces the transaction code at all, which means the reader has no way to tell whether a share-count decline reflects a discretionary sale or a mechanical event without pulling the raw Form 4 and checking Column 4 manually. GeminIQ's Insider Transactions feature pulls directly from the raw SEC Form 4 feed and classifies every row as a Purchase or a Sale, so the direction of the transaction is immediately visible without opening the underlying filing.

That classification is the starting point, not the finish line — the table above still matters for deciding how much weight a Purchase or Sale actually deserves once you know which code produced it. For a full field-by-field walkthrough of everything else on the form, including the footnotes and the 10b5-1 disclosure that determine how much an S transaction really tells you, see How to Read SEC Form 4: Insider Buying and Selling Explained.

Frequently Asked Questions

What is the most important Form 4 transaction code?

Code P — an open-market or private purchase — is the only code that unconditionally represents a voluntary, out-of-pocket capital decision by the insider. No compensation plan, tax obligation, or estate event can generate a P transaction; it only appears when someone chooses to spend their own money on the stock.

What does code F mean on a Form 4?

F is the tax-withholding code, used when a company automatically withholds a portion of newly vested shares to cover the recipient's income tax obligation. It appears as a disposition and reduces share count, but represents no decision by the insider to sell.

What is the difference between codes M and X?

M is the exercise or conversion of a derivative security exempted under Rule 16b-3 — the standard code for exercising employee stock options. X is the exercise of an in-the-money or at-the-money derivative security outside that specific exemption. Functionally, both describe an option exercise; which one applies depends on which SEC rule governs the specific compensation arrangement. In both cases, the exercise itself carries little signal — what matters is whether the resulting shares were sold or retained.

Why do most Form 4 filings use code A or F instead of P or S?

Modern executive compensation is heavily weighted toward RSUs and options rather than cash salary, and both generate routine, scheduled Form 4 filings — an A when the equity is granted, an F when a portion is withheld for taxes at vesting. These filings occur automatically as part of the compensation structure, which is why they vastly outnumber discretionary P and S transactions in raw filing volume.

Can a single Form 4 line have more than one code?

Yes, in one specific case: K is appended alongside another code when the transaction involves an equity swap or similar instrument, producing combinations like "S/K." Outside of that pairing, each line on the form carries one transaction code describing one type of event.

Every one of these questions comes back to the same rule: the code decides whether a transaction means anything — the share count never does.

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