SEC Form 4 Transaction Codes: The Definitive Reference

If you're staring at a Form 4 filing and trying to decode what an insider actually did, the single letter in Column 3 tells you almost everything, provided you know how to read it. This is the complete, plain-English reference to every SEC Form 4 transaction code, grouped the way the SEC itself groups them, with the context the regulator's own glossary leaves out.

Key takeaway: A Form 4 transaction code is a one-letter identifier that classifies each reported change in beneficial ownership. The SEC defines 20 letters across five families, and 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 SEC Form 4 transaction codes?

SEC Form 4 transaction codes are single-letter identifiers that Section 16 insiders (officers, directors, and beneficial owners of more than 10% of a registered equity class) use to characterize each reportable change in beneficial ownership. They appear in Column 3 of Table I (non-derivative securities) and Table II (derivative securities) on Form 4, and the same code set applies to Form 5. The authoritative list lives on the SEC's Ownership Form Codes page.

The codes exist because Section 16(a) of the Securities Exchange Act of 1934 requires insiders to report transactions publicly, and Section 16(b) allows the issuer (or a shareholder acting on its behalf) to recover any "short-swing" profits from matched purchases and sales within six months. Whether a given transaction counts toward that six-month test depends almost entirely on its code, which is why the SEC insists filers pick the right letter and, in some cases, add a footnote explaining themselves.

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

Why the codes exist: Section 16 in one paragraph

Section 16 of the Exchange Act treats corporate insiders as fiduciaries with an information advantage. Subsection (a) forces them to disclose holdings and trades on Forms 3, 4, and 5. Subsection (b) lets the company claw back any profit from opposite-way trades within a six-month window, regardless of intent. Rule 16b-3 then carves out certain issuer-to-insider transactions (grants, tax withholding, plan exercises) that would otherwise trigger 16(b) liability. The transaction codes are how filers signal, in one character, which regulatory bucket a trade belongs to.

Where the code sits on the form

A transaction code by itself is only half the story. On the actual Form 4, each row also carries an A (acquired) or D (disposed) flag, a share amount, a price, a resulting beneficial ownership figure, and any footnotes. Reading the code without those adjacent fields is like reading a verb without a subject.

• Table I captures non-derivative securities (common stock, RSUs that have vested into shares).
• Table II captures derivative securities (options, warrants, convertibles, RSUs pre-vest, equity swaps).
• The 10b5-1 checkbox, added by the SEC's December 2022 final rule and effective for filings on or after April 1, 2023, indicates whether the transaction was made pursuant to a Rule 10b5-1(c) trading plan and requires disclosure of the plan's adoption date.

The checkbox matters because an "S" (sale) executed under a pre-established 10b5-1 plan reads very differently from a discretionary "S" placed the day before earnings. Same letter, different signal.

The full list: all 20 Form 4 transaction codes

The SEC groups the codes into five families. Here is every code, its plain-English meaning, the section of the rules that authorizes it, and what it typically signals to a reader.

Source: SEC Ownership Form Codes. Note that the SEC's page lists 20 letters; some references cite 19 because "V" functions as a modifier rather than a standalone transaction type.

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

These are the codes an equity analyst actually cares about, because they are the only ones that reflect an unforced market decision.

P (Purchase) 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. There is no vesting schedule, no compensation plan, no tax obligation forcing 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" (Investor Bulletin).

S (Sale) is the mirror image, but noisier. Insiders sell for many reasons that have nothing to do with a view on the stock: liquidity, diversification, a scheduled 10b5-1 plan, a house purchase. The 10b5-1 checkbox (post-April 2023) is the critical modifier. An S with the box checked and a plan-adoption date months in the past is a mechanical event; an S with no checkbox is discretionary.

V (Voluntary) is not a transaction type at all. It is a timing flag that says the filer reported this transaction earlier than the rules required, typically because a small transaction that would otherwise wait for Form 5 was disclosed on Form 4 instead. Read the paired code to understand what actually happened.

Family 2: Rule 16b-3 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, which is why they get their own family.

• A (Grant/Award): The compensation committee awarded equity. Common on the day RSUs, options, or PSUs are issued. Zero discretion by the insider.
• D (Disposition to Issuer): Shares go back to the company, typically unvested RSUs forfeited on departure or shares surrendered under a plan provision.
• F (Payment via Withholding): The most misread code on Form 4. When RSUs vest or options are exercised, the insider owes ordinary income tax. Rather than writing a check, the company withholds shares equal to the tax liability. F is not a sale. The insider never received cash from a market transaction. Retail commentary that flags an F filing as "insider dumping" is almost always wrong.
• I (Discretionary Plan Transaction): Usually a 401(k) or deferred-compensation election into or out of a company-stock fund.
• M (Exercise/Conversion): The mechanical act of exercising an option or converting a derivative. What matters is what happens next. An M paired with a same-day S is an exercise-and-sell (cash out, no equity retained). An M with no follow-on S means the insider kept the shares, which is a very different signal from the same option exercise.

The M+F and A+F patterns

Two pairings dominate real-world filings and confuse first-time readers:

1. A followed by F on vesting day. RSUs vest (A, though sometimes the original grant was the A and vesting is reported differently). The company withholds shares for taxes (F). Net share change is smaller than either number alone.
2. M followed by F, then S. Options are exercised (M). Shares are withheld to cover the exercise price and tax (F). Remaining shares are sold to fund the exercise or diversify (S). The S here is often part of a pre-set cashless exercise, not a market call.

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

These are the non-16b-3 vocabulary for options, warrants, convertibles, and similar instruments in Table II. Most are mechanical and carry limited signal on their own.

• C: A convertible security (preferred stock, convertible note) converts into common per its terms.
• E: A short derivative position expires unexercised.
• H: A long derivative position expires or is cancelled with value received.
• O: Exercise of an out-of-the-money derivative. Unusual enough that the footnote is worth reading.
• X: Exercise of an in-the-money or at-the-money derivative, outside a 16b-3-exempt plan.

Family 4: Other 16(b)-exempt and small acquisitions (G, L, W, Z)

• G (Gift): Bona fide gifts of securities. Since the SEC's 2022 amendments, insider gifts must be reported on Form 4 within two business days, closing a prior loophole where gifts could sit on Form 5 for months.
• L (Small Acquisition): A purchase from the issuer under $10,000 in a six-month window, per Rule 16a-6. These typically go on Form 5.
• W (Will / Descent): Estate transfers.
• Z (Voting Trust): Deposits into or withdrawals from a voting trust arrangement.

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

The catch-alls. These three codes carry disproportionate risk for filers because the SEC and academic researchers scrutinize them.

J (Other) is the residual category, used when no other code fits. The SEC's own definition, "Other acquisition or disposition (describe transaction)," bakes in a mandatory footnote. A J filing without a substantive footnote is defective on its face. J has drawn particular regulatory attention: a 2024 Harvard Business Law Review study of J-coded transactions since 1992 argued that some filers use the code to obscure the nature of trades that would otherwise be coded S, and called on the SEC to treat suspicious J filings as enforcement priorities.

K (Equity Swap) flags hedging or swap transactions. Because many public companies now prohibit executives from hedging their equity compensation, a K filing is a governance flag that IR and proxy advisors will notice.

U (Tender) is used when shares are tendered in a change-of-control transaction. It is event-driven, not a discretionary market trade.

Modifiers: V, K appended, and delinquency flags

A handful of code combinations use one letter as a modifier on another:

• "V" paired with the underlying code signals voluntary early reporting of a transaction that could have waited.
• "K" appended to another code (e.g., "J/K") indicates the transaction involved an equity swap that also fits another category.
• Delinquency flags: some filing software appends a "4" or "5" to the code (e.g., "A4") to indicate the transaction is being reported late on a Form 4 or Form 5. Late filings trigger disclosure under Item 405 of Regulation S-K in the issuer's next proxy statement.

Filing mechanics: who, when, where

Who must file: officers, directors, and beneficial owners of more than 10% of any class of a company's registered equity securities.

When: Form 4 must be filed before the end of the second business day following the transaction date, per Rule 16a-3(g). Form 3 is due within 10 days of becoming an insider. Form 5 is due no later than 45 days after the issuer's fiscal year-end and uses the same transaction codes.

Where: Electronically via EDGAR, absent a hardship exemption (General Instructions to Form 4).

For Finrep's side-by-side deadline comparison across the three forms, see Form 3 vs Form 4 vs Form 5: 2026 SEC Insider Reporting Guide.

How to read a Form 4 in four steps

1. Identify the reporting person and relationship (officer, director, 10% holder) in Item 1.
2. Check the 10b5-1 checkbox at the top. If checked, note the plan adoption date. This reframes any S or M+S below.
3. Read each transaction row as a sentence: [Date] the insider [A/D flag] [amount] shares via [code], at [price], leaving [resulting ownership]. If the code is J, read the footnote before drawing any conclusion.
4. Look for paired rows on the same date. M+S same-day means cash-out. A+F on vesting day means tax withholding. Isolated P or discretionary S carries the most weight.

Common filer errors that trigger real consequences

Warning: The wrong code is not a cosmetic error. It can defeat a Rule 16b-3 exemption, expose the insider to Section 16(b) disgorgement, and force the issuer to disclose a delinquency in its next proxy under Item 405.

• Using J when a specific code fits. If the transaction is a gift, use G. A tender, U. A swap, K. J is a last resort.
• Coding a 10b5-1 sale as J. The correct code is S with the checkbox and plan-adoption date.
• Miscoding an F as an S. Tax withholding is not a market sale and should never be coded S.
• Missing footnotes on J filings. The SEC's definition itself requires the description; omission is a defective filing.
• Late filing without appending the delinquency modifier, and failing to flag the delinquency for Item 405 disclosure.

FAQ

What are transaction codes on a Form 4? They are single-letter SEC-defined identifiers in Column 3 of Form 4 that classify each reported change in beneficial ownership. There are 20 codes across five families, and each one tells the reader whether the transaction was a market trade, a compensation event, an exempt disposition, or something else entirely.

What does code F mean on a Form 4? Code F reports the payment of an option exercise price or tax liability by delivering or withholding securities incident to the receipt, exercise, or vesting of a security issued under Rule 16b-3. In plain terms, the company withheld shares to cover the insider's tax bill. It is exempt from Section 16(b) and is not an open-market sale.

What is code M on a Form 4? Code M reports the exercise or conversion of a derivative security exempted under Rule 16b-3, typically an option exercise or RSU conversion. On its own, M is mechanical. When M is followed by an S on the same or next business day, the insider exercised and immediately sold; when M appears alone, the insider kept the underlying shares.

How do I read a Form 4 SEC filing? Start with the reporting person's relationship to the issuer, check the 10b5-1 checkbox and any plan adoption date, then read each transaction row as: date, A or D flag, share amount, transaction code, price, and resulting beneficial ownership. Read footnotes for any J-coded row, and look for same-date paired codes (M+S, A+F) that reveal the full economic picture.

Which Form 4 codes represent real insider selling? A discretionary S (open-market sale with no 10b5-1 checkbox) is the clearest bearish signal. An S under a 10b5-1 plan is a scheduled sale and carries less discretionary information. F, M, D, and A are compensation mechanics, not insider selling, even though they can appear as large dispositions on the filing.

Are all Form 4 transaction codes exempt from Section 16(b) short-swing profit recovery? No. The Rule 16b-3 family (A, D, F, I, M) and the "other exempt" family (G, L, W, Z) are generally exempt when their conditions are met. General codes (P, S) and the derivative and "other" codes are not automatically exempt and can be matched against opposite-way trades within six months for 16(b) disgorgement.

Bookmark the SEC's Ownership Form Codes page for the authoritative letter list, and treat every J-coded row as a filing that needs its footnote read.