What is the most important field on a Form 4?

The transaction code. A one-letter code in Table I distinguishes an open-market purchase (P) — someone spending their own money — from a grant (A), an option exercise (M) or tax withholding (F), none of which are decisions to trade. Reading direction (acquired or disposed) without reading the code is the most common mistake.

What does 'shares owned following transaction' tell you?

The insider's total reported holding of that security after the trade. Comparing the transaction size to this number is how you tell a position-changing trade from a rounding error against a very large holding.

Does the 10b5-1 checkbox appear on every Form 4?

As a machine-readable field, only since EDGAR release 23.1 in March 2023. On older filings the only evidence that a trade was pre-scheduled is a footnote mentioning a trading plan or Rule 10b5-1.

How to Read an SEC Form 4, Field by Field

Form 4 is a short document. That is the problem with it: every field is load-bearing, and two or three of them decide whether a filing means anything at all. Most people read the direction — shares went in, shares went out — and stop. The direction is the least informative part.

Here is a worked example. Every field is clickable; start with the transaction code, which is where anyone experienced starts.

Form 4 — Statement of Changes in Beneficial Ownership

Issuer:

Reporting person:

Table I — Non-Derivative Securities

Transaction code

A one-letter code for the kind of transaction. P is an open-market purchase — the insider paid the market price with their own money. Most codes are not that: A is a grant, M an option exercise, F tax withholding.

This single letter is the difference between a decision to buy and the company handing someone shares. It is the first thing to read on any Form 4.

Read these three first

The transaction code. One letter, in Table I. P is an open-market purchase — the insider paid the prevailing price with their own money. Almost nothing else is a decision to trade: A is a grant, M is an option exercise, F is shares withheld to pay tax on a vesting award. A filing can show a large acquisition and contain no buying whatsoever.

Shares owned following the transaction. This is the insider's total holding after the trade. A $50,000 purchase means one thing when it lifts someone from 2,000 shares to 3,200, and something else entirely against a two-million-share position. The transaction line alone cannot tell you which; this field can.

The 10b5-1 checkbox, and the footnotes. A ticked box means the trade fired from a plan set up in advance — the decision was made months ago, and the filing tells you little about what the insider thinks now. Before March 2023 there is no box, so the footnotes are the only place a plan gets mentioned.

The fields that mislead

Acquired / Disposed. A purchase and a grant are both "acquired". A sale and a tax withholding are both "disposed". Direction tells you which column the shares moved in, not why.

Price. For a grant or a gift this is often $0 or blank — which does not mean shares were free in any meaningful sense, only that no market transaction set a price. For a purchase or sale it is the real number.

Reporting person. The name in this box is frequently an institution — a fund, a bank, a market maker that has crossed 10% ownership — not a person exercising judgement. The most prolific filers on EDGAR are entities running broad books, and a $2M purchase from one of them is not the same signal as a founder-CEO stepping in with personal money.

Why this matters

Insider-trading data is mostly noise, and the noise is legible only if you read the form properly. A site that shows you "acquisitions" without separating purchases from compensation is showing you a stream that is roughly 90% pay events and calling it insider buying.

Every transaction on this site links back to the original Form 4 on SEC EDGAR. If a figure here disagrees with the filing, the filing wins.

The short version

A Form 4 has maybe six fields that matter and two that actively mislead. Read the transaction code first, check the size against shares owned after, and look for a trading-plan flag before you conclude anything. Everything else is detail.