Form 4 Transaction Codes Explained: All 20 SEC Codes

The single letter in Column 3 of a Form 4 filing tells you more than the share count does. It tells you whether an insider spent personal capital, received a compensation grant, paid a tax bill, or did something unusual enough to require a footnote. Get the code wrong and you misread the signal entirely.

The SEC defines exactly 20 transaction codes across five families. This article explains all 20 in plain English, flags the most commonly misread ones, and covers the post-April 2023 10b5-1 checkbox that fundamentally changed how sales codes should be interpreted.

Key takeaway: A Form 4 transaction code is a one-letter identifier that classifies each reported change in beneficial ownership. The letter determines whether the transaction is a real market signal, a compensation mechanic, or an exempt event that never touched the open market.

What Are Form 4 Transaction Codes?

Form 4 transaction codes are single-letter identifiers that Section 16 insiders must use to classify each reportable change in beneficial ownership. Section 16 insiders are officers, directors, and beneficial owners of more than 10% of a registered equity class.

The codes appear in Column 3 of Table I (non-derivative securities, such as common stock) and Table II (derivative securities, such as options, warrants, and convertibles) on Form 4. The same code set applies to Form 5.

They exist because Section 16 of the Exchange Act does two things: subsection (a) forces insiders to disclose holdings and trades publicly, and subsection (b) lets the company claw back any profit from opposite-way trades within a six-month window, regardless of intent. Whether a given transaction counts toward that six-month short-swing profit test depends almost entirely on its code. Rule 16b-3 then carves out certain issuer-to-insider transactions (grants, tax withholding, plan exercises) that would otherwise trigger Section 16(b) liability. The codes are how filers signal, in one character, which regulatory bucket a trade belongs to.

For the full legal treatment of exemption mechanics and 16(b) exposure, see Finrep's Section 16 Transaction Codes: 2026 Complete Guide. This article stays on the definitional layer: what each code means, why it exists, and how to read it.

How to Read a Form 4 Row: The Three-Part System

A transaction code alone is only part of the story. Each row on Form 4 also carries:

• The A/D flag (Acquired or Disposed): the code tells you the type of transaction; the A/D flag tells you the direction. A gift (code G) can be either an acquisition or a disposition depending on which way the shares moved. Reading the code without the A/D flag is analytically incomplete.
• The 10b5-1 checkbox: added by the SEC's December 2022 final rule (Release No. 33-11138), effective for Form 4 filings on or after April 1, 2023. It requires disclosure of whether a transaction was made pursuant to a Rule 10b5-1(c) trading plan and, if so, the date the plan was adopted.

An "S" (sale) executed under a pre-established 10b5-1 plan with an adoption date months in the past is a mechanical, pre-planned event. An "S" with no checkbox is a discretionary sale. Same letter, very different signal. Most reference articles on Form 4 codes predate this rule or ignore it entirely.

For a practitioner walkthrough on selecting the correct code and avoiding amendment triggers, see Form 4 Transaction Codes: 2026 Practitioner Walkthrough.

All 20 Form 4 Transaction Codes: Quick Reference

The SEC groups the 20 codes into five families. The table below lists every code, its plain-English meaning, and its signal weight for investment or compliance purposes.

Source: SEC Ownership Form Codes

Family 1: General Transaction Codes (P, S, V)

These are the codes an equity analyst actually cares about first, because they are the only ones that can, on their own, reflect a voluntary market decision.

P: Open Market Purchase

P is the cleanest bullish signal on Form 4. The insider spent personal capital to acquire securities on the open market or in a private deal. No vesting schedule delivered the shares, no compensation plan required the purchase, no tax obligation forced the trade. As the SEC's Office of Investor Education notes, "reports of insiders' purchases and sales of company securities can provide useful information as to insiders' views of the performance or prospects of the company."

When screening for insider conviction, P is the code to weight most heavily. A CEO who buys 25,000 shares at $45 on the open market has deployed $1.125 million of personal capital at the same price any public investor would pay.

S: Open Market Sale

S is the mirror image of P, but far noisier. The insider sold shares on the open market or in a private transaction. The problem is that insiders sell for many reasons unrelated to a negative view on the stock: liquidity, diversification, tax planning, a house purchase, or a pre-scheduled 10b5-1 plan. The SEC's own investor bulletin explicitly notes that "insiders may sell company securities for any number of reasons, including for liquidity and diversification purposes."

Post-April 2023, the 10b5-1 checkbox is the critical modifier. An S with the box checked and a plan-adoption date that predates the trade by months (subject to the 120-day cooling-off period for officers and directors under the December 2022 amendments) is a mechanical event. An S with no checkbox is discretionary and carries more interpretive weight.

V: Voluntarily Reported Earlier Than Required

V is not a transaction type. It is a timing modifier. It means the filer chose to report a transaction on Form 4 that could have waited for Form 5. The actual transaction type is indicated by the code paired with V in the same row. Read the paired code to understand what happened; V only tells you when it was reported.

Family 2: Rule 16b-3 Transaction Codes (A, D, F, I, M)

These five codes cover the plumbing of modern executive compensation. Rule 16b-3 exempts qualifying issuer-to-insider transactions from Section 16(b) short-swing profit recovery, recognizing that compensatory grants and plan-related transactions are not the speculative insider trading that Section 16(b) was designed to deter. None of these codes reflect a discretionary market decision by the insider.

A: Grant or Award

A means the compensation committee awarded equity. RSU grants, option awards, performance share units, and other equity compensation issued under a company plan all carry code A. The insider exercised zero discretion; the board or compensation committee initiated the transaction. A large A transaction is the most common reason a Form 4 shows a big share count with zero investment signal.

D: Disposition to Issuer

D means shares went back to the company. The most common scenarios are unvested RSUs forfeited on departure, shares surrendered under a clawback provision, or shares returned under a specific plan term. This is an employment event, not a market view.

F: Payment via Tax Withholding

F is the most misread code on Form 4. When RSUs vest, the insider owes income tax on the value of the shares received. Rather than the insider writing a check, the company withholds a portion of the shares automatically to cover that tax bill. The insider never receives those shares and never sells them on the open market.

A concrete example: an executive's 10,000 RSUs vest at $50 per share. The company withholds 3,500 shares (35% effective tax rate) under code F. The executive receives 6,500 shares. The F transaction shows a disposal of 3,500 shares, but no cash changed hands and no open-market sale occurred. Misreading F as a bearish signal is a common and significant analytical error.

I: Discretionary Plan Transaction

I covers discretionary transactions inside a tax-conditioned employee benefit plan, such as a 401(k) that holds company stock. The insider elects to move money into or out of the company stock fund. This is relatively rare and carries limited signal because plan rules and required cooling-off periods between opposite-direction elections constrain the insider's discretion.

M: Exercise of Exempt Derivative (Compensatory Option)

M covers the exercise of a derivative security that is itself exempt under Rule 16b-3, most commonly a compensatory stock option. The insider acquires shares by paying the exercise price (or via a cashless exercise), but the underlying option was a compensation grant, not a market purchase.

M is frequently paired with a same-day S in a cashless exercise: the insider exercises options (M), acquires shares, and immediately sells enough shares (S) to cover the exercise price and taxes. The net economic acquisition is small or zero. Readers who see only the S without the paired M will dramatically overestimate the insider's selling activity. An M with no corresponding S, by contrast, means the insider kept the shares and is a meaningfully more bullish signal.

Key distinction: M applies to compensatory derivatives exempt under Rule 16b-3. X applies to non-exempt derivatives such as warrants acquired in a market transaction. These are frequently confused but have different Section 16(b) implications.

Family 3: Derivative Securities Codes (C, E, H, O, X)

These five codes cover derivative transactions that are NOT exempt under Rule 16b-3. They appear primarily in Table II of Form 4.

C: Conversion of Derivative Security

C covers conversion of a non-exempt derivative into the underlying security, such as a convertible note or convertible preferred share converting into common stock. This is contractual mechanics per the instrument's terms, not a discretionary market decision.

E: Expiration of Short Derivative Position

E covers the expiration of a short derivative position, such as a written call option that expires worthless. This is a relatively rare code in practice.

H: Expiration of Long Derivative with Value Received

H covers the expiration or cancellation of a long derivative position where the insider received value, such as a long put that expires in-the-money and is cash-settled. This is distinct from E (short position expiration) and O (exercise of an out-of-the-money derivative).

O: Exercise of Out-of-the-Money Derivative

O covers exercise of a derivative that is out-of-the-money at the time of exercise. Exercising an out-of-the-money option is economically irrational in most circumstances, so O typically appears near expiry when the insider has no better option, or under a specific plan provision that forces exercise.

X: Exercise of In-the-Money or At-the-Money Derivative

X is the most common derivative exercise code for non-exempt derivatives, such as warrants acquired in a market transaction. It covers exercise of an option or warrant that is in-the-money or at-the-money. The key distinction from M: X applies to derivatives that are NOT exempt under Rule 16b-3, which means the exercise can count toward the Section 16(b) six-month matching test.

Family 4: Other Section 16(b) Exempt and Small Acquisition Codes (G, L, W, Z)

These four codes cover transactions that are exempt from Section 16(b) short-swing profit recovery but still reportable under Section 16(a). None carry a market signal.

G: Bona Fide Gift

G covers gifts of securities by or to the insider. The direction (given or received) is indicated by the A/D flag. Gifts are typically estate planning, charitable giving, or transfers to family trusts. They are exempt from Section 16(b) but must be reported on Form 4 (or Form 5 for small gifts). The SEC's 2022 rulemaking tightened gift reporting, requiring Form 4 disclosure within two business days rather than allowing deferred Form 5 reporting.

L: Small Acquisition under Rule 16a-6

L covers acquisitions that qualify for the Rule 16a-6 de minimis exemption: purchases of less than $10,000 in a six-month period that need not be reported on Form 4 when they occur but must appear on Form 5. When reported on Form 4 voluntarily, L is often paired with V.

W: Acquisition or Disposition by Inheritance

W covers shares acquired or disposed of through a deceased person's estate, under a will or the laws of descent and distribution. This is a purely administrative event with no market signal and is exempt from Section 16(b).

Z: Voting Trust Deposit or Withdrawal

Z covers the deposit of shares into, or withdrawal from, a voting trust arrangement. This changes the form of ownership but not the economic interest. It is exempt from Section 16(b) and carries no investment signal.

Family 5: Other Transaction Codes (J, K, U)

These three codes cover transactions that do not fit neatly into the other four families. Two of them warrant close attention.

J: Other Acquisition or Disposition

J is the catch-all code for any transaction that does not fit another category, and it must be accompanied by a footnote describing the transaction. J may cover unusual compensation arrangements, court-ordered transfers, divorce settlements, fund distributions of portfolio securities, or transactions the filer could not fit into another code.

J is a red flag for complexity. A 2024 Harvard Business Law Review study compiled a database of substantially all insider dispositions reported using code J since 1991 (180,970 transactions involving $3.4 trillion in value) and found that, on average, these transactions yielded significant abnormal profits, suggesting J-coded transactions are often timed to precede negative news. The authors called on the SEC to treat miscoding as a potential 10b-5 violation and to scrutinize late-filed J-coded transactions as highly suspicious.

When you see a J code, read the footnote carefully. If there is no footnote, or the footnote is vague, that is itself a compliance deficiency. Late-filed J-coded transactions are a particular red flag given the two-business-day filing deadline that has applied since the Sarbanes-Oxley Act (Section 403, effective August 2002).

K: Equity Swap or Similar Instrument

K covers equity swaps and instruments with similar characteristics. The SEC's investor bulletin specifically calls out K as relevant to assessing an insider's true economic exposure: investors should consider "the extent of insiders' economic stake in the success of the company, as reflected both in outright ownership and transactions (such as equity swaps) that may hedge the economic risk of that ownership."

An insider can hold a large nominal share position while using a K-coded swap to hedge away all economic risk, making their reported ownership misleading as a conviction signal. K transactions warrant scrutiny beyond the share count.

U: Tender in Change of Control Transaction

U covers shares tendered in a merger or acquisition tender offer. This is a corporate event-driven disposition, not a discretionary sale, and is exempt from Section 16(b). U appears primarily during M&A activity and carries no signal about the insider's view of the company's standalone value.

Which Codes Signal Genuine Conviction?

Not all codes are equal for investment or compliance analysis. Here is a practical signal-strength framework:

High signal (genuine market conviction):

• P: Insider spent personal capital at market prices. The strongest bullish signal.
• S (without 10b5-1 checkbox): Discretionary sale. Warrants investigation of size, timing, and pattern.

Compensation mechanics (no market signal):

• A: Equity grant from compensation committee.
• M: Option exercise (especially when paired with same-day S).
• F: Tax withholding at vesting. Not a sale.
• D: Shares returned to company.
• I: Plan-based discretionary transaction.

Exempt housekeeping (no market signal):

• G: Gift (estate planning).
• W: Inheritance.
• Z: Voting trust change.
• U: M&A tender.
• L: De minimis acquisition.

Requires further investigation:

• J: Catch-all with footnote. Read the footnote; flag if absent or vague.
• K: Equity swap. Check whether the insider is hedging economic exposure.
• S (with 10b5-1 checkbox): Pre-planned sale. Check the plan adoption date and the cooling-off period.

Form 4 Transaction Codes: FAQ

What does transaction code G mean on Form 4? G means the insider gave shares as a bona fide gift or received shares as a gift. The A/D flag tells you the direction. Gifts are exempt from Section 16(b) short-swing profit recovery but must still be reported. Most G transactions are estate planning or charitable transfers.

What does code J mean on Form 4? J is the catch-all code for any transaction that does not fit another category. It must be accompanied by a footnote explaining the transaction. J is a red flag for complexity and, in some cases, for potential miscoding. Always read the footnote; a missing or vague footnote is itself a compliance problem.

What is transaction code M on Form 4? M means the insider exercised or converted a derivative security (most commonly a compensatory stock option) that is exempt under Rule 16b-3. It is a compensation mechanic, not a market purchase. When M is immediately followed by an S on the same day, the insider ran a cashless exercise and may have retained little or no net equity.

What is transaction code F on Form 4? F means the company withheld shares to cover the insider's tax liability when equity compensation vested or was exercised. The insider never received those shares and never sold them on the open market. F is not a bearish signal; it is a tax event.

How do I tell if an insider sale (S) was discretionary or pre-planned? Check the 10b5-1 checkbox added to Form 4 by the SEC's December 2022 final rule, effective for filings on or after April 1, 2023. If the box is checked and the plan adoption date predates the trade by at least 120 days (for officers and directors), the sale was pre-planned. If the box is unchecked, the sale was discretionary.

What is the difference between M and X on Form 4? Both involve exercising a derivative, but M applies to derivatives that are exempt under Rule 16b-3 (compensatory options and similar grants), while X applies to non-exempt derivatives such as warrants acquired in a market transaction. X exercises can count toward the Section 16(b) six-month matching test; M exercises cannot.

Where is the authoritative list of all Form 4 transaction codes? The SEC's Ownership Form Codes page is the primary source. The General Instructions to Form 4 provide additional context. All 20 codes are defined there.

For the compliance officer's perspective on selecting the right code and avoiding late-filing penalties, see Form 3 vs Form 4 vs Form 5: 2026 SEC Insider Reporting Guide and SEC Form 5 Filing Requirements: 2026 Practitioner Walkthrough.