SEC Form 4, explained: how to read an insider trading filing

Form 4 is how corporate insiders disclose their trades within two business days. Here's what every box and transaction code means, and how to tell a meaningful buy from routine compensation.

2026-08-05 · 13 min read · By Insider Option

Congressional trades get the headlines, but corporate insider filings are the richer dataset: they arrive in two business days rather than 45, they contain exact share counts and prices rather than dollar ranges, and there are tens of thousands of them a year. That filing is Form 4.

The catch is that most Form 4s are meaningless. They report option grants, vesting events, and tax withholding — mechanical consequences of a compensation package, not decisions. Learning to read a Form 4 is mostly learning to discard the noise.

Who has to file, and why

Section 16 of the Securities Exchange Act of 1934 applies to three groups, collectively "Section 16 insiders":

• Officers — CEO, CFO, and other policy-making executives.
• Directors — every member of the board.
• Beneficial owners of more than 10% of any registered class of the company's equity.

These people must report any change in their ownership of the company's securities. The deadline is two business days after the transaction — tightened from the old ten-day, month-end regime by Sarbanes-Oxley in 2002, which is why insider data before and after 2003 is not really comparable.

The three Section 16 forms

• Form 3 — initial statement of ownership, filed when someone first becomes an insider (new hire, new board seat, crossing 10%).
• Form 4 — a change in ownership. This is the one you care about.
• Form 5 — annual catch-up for small or exempt transactions that were not required to be reported on a Form 4, due 45 days after fiscal year end. A Form 5 that contains something interesting is often a late Form 4 in disguise.

Reading the form, box by box

A Form 4 has a header and two tables. Everything meaningful is in Table I.

Header

• Reporting person and issuer — who traded, in what company.
• Relationship — checkboxes for Director, Officer (with title), 10% Owner, Other. A CEO buying is a different signal from a newly seated director buying.
• Date of earliest transaction — compare it to the filing date. A gap wider than two business days is a late filing.
• Joint/group filing — often present when a fund files for multiple affiliated entities.

Table I — non-derivative securities

Common stock, directly. The columns that matter:

• Transaction date — when it happened, not when it was filed.
• Transaction code — the single most informative field. See the table below.
• Amount, and (A) or (D) — share count, acquired or disposed.
• Price — the actual execution price, or a weighted average with a footnote giving the range. Real numbers, unlike Congressional disclosures.
• Shares owned following the transaction — the denominator. This is what turns a raw share count into a meaningful figure.
• Direct (D) or indirect (I) — indirect means held through a trust, LLC, family partnership, or spouse. Indirect holdings are still the insider's economic exposure but the decision-maker may not be.

Table II — derivative securities

Options, warrants, RSUs, convertibles. Adds an exercise price, an exercisable date, and an expiration date. Most compensation activity lives here, and most of it is uninformative.

Transaction codes: the ones that matter

The code is where the signal is. Grouped by how much they actually tell you:

High information

• P — Purchase. An open-market buy. The insider chose to convert their own cash into more exposure to a company they already have concentrated career risk in. This is the code that the academic literature finds predictive.
• S — Sale. A disposal. Informative only in context — check the 10b5-1 checkbox first (see below).

Low information (compensation mechanics)

• A — Grant or award. The company gave them shares. Not a decision.
• M — Exercise of a derivative. Converting options into shares. Often immediately followed by an S as the insider sells to cover.
• F — Shares withheld for tax. Pure mechanics on a vesting event. Appears as a disposal and routinely gets miscounted as "insider selling" by low-quality screeners.
• G — Gift. Estate planning or charity.
• D — Disposition to the issuer. Usually a buyback or cancellation.
• C — Conversion. A convertible security becoming stock.

Context-dependent

• X — Exercise of an in-the-money option. Timing can matter when done well before expiry.
• J — Other. Requires a footnote. Read the footnote; J is where the unusual things hide.

The single most common analytical error is treating aggregate "insider selling" as bearish without filtering out A, M, F, and G. Once you keep only P and S, the picture usually changes completely — and often the "wave of insider selling" in a headline is a vesting date.

The 10b5-1 checkbox

Since 2022, Form 4 has an explicit checkbox indicating the transaction was made under a Rule 10b5-1 trading plan — a pre-arranged schedule adopted while the insider was not in possession of material non-public information.

This is the highest-value field on the form after the transaction code. A sale under a 10b5-1 plan was decided months ago and tells you nothing about the insider's current view. A discretionary sale, off-plan, right after an earnings release, is a different object entirely.

SEC amendments effective in 2023 added cooling-off periods (generally 90–120 days between adopting a plan and trading under it) and required disclosure of plan adoption and termination. Termination of a plan before it completes is an underrated thing to watch.

Form 4 vs the other filings people confuse it with

• Form 144 — a notice of intent to sell restricted securities. It precedes a sale and may never be followed by one. Form 4 reports a sale that happened.
• Schedule 13D/13G — filed on crossing 5% ownership. 13D signals activist intent; 13G signals passive. Different threshold, different purpose.
• Form 13F — quarterly institutional holdings, 45 days after quarter end. Positions, not transactions. See our 13F guide.
• Periodic Transaction Report — the Congressional equivalent. 45-day deadline, dollar ranges instead of exact prices. See the PTR guide.

Where to get the data

EDGAR at sec.gov is the source. Three routes:

1. Company filing history — filter by form type "4" on any issuer's EDGAR page.
2. Full-text search at efts.sec.gov/LATEST/search-index for cross-company queries.
3. Daily index files — every filing accepted each day, which is what you want if you are building a pipeline. Form 4s are filed as structured XML, so unlike House PTRs there is no OCR problem: the data is clean by construction.

The SEC requires a descriptive User-Agent header identifying you and rate-limits to roughly ten requests per second. Ignore either and you will be blocked.

A practical filter

If you want to reduce tens of thousands of annual Form 4s to something you can actually read, this is a defensible starting screen:

• Transaction code P only.
• Not flagged as a 10b5-1 plan transaction.
• Dollar value that is material relative to the insider's stated compensation — a $2m buy by a CEO earning $1m matters; a $20k buy does not.
• A meaningful increase in shares held — use the "shares owned following" column, not the raw purchase size.
• Bonus signal: multiple distinct insiders buying within the same few weeks. Cluster buying is consistently the strongest form of this signal in the research.

Whether that screen actually produces excess returns — and what the published research says about it — is the subject of do insider buys actually predict stock returns?

This post is for informational purposes only and is not legal or investment advice. See our disclaimer.