How Do You Read an SEC Form 4 Filing to See Real Insider Buying?

"Insider buys $2 million of stock" is a headline that moves small caps. Often the Form 4 behind it shows something else: an option exercise, a grant, or shares withheld for tax. Five minutes with the form tells you which.

What people on X are asking

In October 2026 a research account asked what it tells you when different insiders buy the same stock within days of each other, and how cluster buying is screened from SEC Form 4 filings. In March 2026 an AI prompt thread suggested pasting Form 4 filings and asking the model to ignore routine automated sales under 10b5-1 plans and find cluster buys. And in January 2025 a post asked what it means when an insider sells shares, citing a director's $2.67 million sale. All of that starts with reading the form correctly.

The fact-checked answer

What Form 4 is. Officers, directors and holders of more than 10% of a company's shares are insiders for this purpose. The SEC's investor bulletin explains that in most cases, when an insider trades, they must file a Form 4 within two business days of the transaction, showing the amount bought or sold and the price per share, and that each transaction is coded to show its nature. Filings are public on the SEC's EDGAR system. Legal insider trading of this kind is different from illegal trading on material non-public information; see Investor.gov's definition of insider trading.

Where to look on a Form 4

Based on the SEC's Form 4 and the Investor.gov bulletin. Footnotes often explain price ranges, plan dates and indirect holdings. Tap a column header to sort.

Box or column	What it tells you
Box 1: Name of reporting person	Who traded
Box 2: Issuer name and ticker	Which company
Box 3: Date of earliest transaction	When the first trade on the form happened
Box 5: Relationship	Director, officer (with title), 10% owner or other
Rule 10b5-1 checkbox	Whether the trade was under a pre-arranged trading plan
Table I, column 3: Transaction code	What kind of transaction (see codes below)
Table I, column 4: Amount, (A) or (D), price	Shares acquired or disposed of, and the price
Table I, column 5: Amount owned following	Holdings after the trade
Table I, column 6: D or I	Owned directly, or indirectly (trust, spouse, fund)
Table II	Options, warrants and other derivatives

Common transaction codes (SEC ownership form codes)

Codes from the SEC's EDGAR ownership form code list and the Investor.gov bulletin. V marks a transaction reported earlier than required. Tap a column header to sort.

Code	Meaning	Signal value
P	Open market or private purchase	Highest: the insider chose to spend money
S	Open market or private sale	Mixed: many reasons to sell
A	Grant or award from the company	Low: compensation
M	Exercise or conversion of a derivative (e.g. options)	Low on its own; check for a same-day S
F	Shares withheld to pay exercise price or tax	Low: routine
G	Bona fide gift	Low
J	Other (explained in a footnote)	Read the footnote

Reading a real buy. A meaningful purchase line looks like: code P, (A), a price, and an amount owned afterwards noticeably higher than before. Divide the purchase by the prior holding: a CEO adding 50% to a 100,000-share stake says more than adding 1% to a 5-million-share stake. Check Box 5: purchases by CEOs and CFOs are usually watched more than those of 10% fund owners, who trade for portfolio reasons.

Reading a sale. Sales have many routine causes: diversification, taxes, buying a house. Look for the 10b5-1 checkbox. The SEC's guide to its 2022 amendments explains that, for Forms 4 filed from April 1, 2023, insiders must indicate whether a reported transaction was made under a plan intended to satisfy Rule 10b5-1(c) and give the plan's adoption date. Plan sales were scheduled in advance, so they carry less information. Several unplanned sales by several officers is a different picture.

Cluster buying. When several insiders buy with code P within days, as the first X post above describes, it is a stronger signal than one purchase, because it is less likely to be one person's personal reasons. It is still not a forecast: insiders can be wrong, and buying after a fall can continue to fall. Also check whether the buys were part of an offering or a rights issue, explained in footnotes.

What Form 4 cannot tell you. It does not tell you why. A two-business-day lag means the price may have moved already. Large holders that are funds may hold derivatives in Table II that change the picture. For the financial side of a company, see how to read an earnings report and what EPS is; for buybacks, which are company purchases rather than insider purchases, see what a stock buyback is. Small-cap insider headlines are a favourite tool of pump promoters; see are penny stocks worth it.

Free PDF

Form 4 reading checklist (PDF)

Use this on each filing before acting on an insider headline.

Filing details

Table I

Context

1. Was the Rule 10b5-1 box checked? Plan adoption date in footnotes
2. Any derivative transactions in Table II (M, X, C codes)
3. Other insiders filing P or S in the same weeks
4. Footnotes: price ranges, offerings, trusts

Fill-in fields in the PDF: Company, ticker and filing date; Insider name and relationship (Box 5); Date of earliest transaction (Box 3) and days until filing; Transaction code(s) and (A) or (D); Shares and price for each line; Amount owned following, and % change in holding; Direct (D) or indirect (I) ownership.

Download the PDF (44 KB, made by UXS, no sign-up)

Fund holdings are reported much more slowly; see why 13F data is already out of date.

Insider selling often clusters after a new listing; see what happens when an IPO lockup period ends.

Decision helper

Common mistakes

• Treating code A or M as "insider buying".
• Ignoring the size relative to existing holdings.
• Reading a 10b5-1 plan sale as a warning.
• Acting on a headline without opening the filing.

FAQ

What is SEC Form 4?

A report of an insider's change in ownership, filed within two business days of the trade.

What does code P mean on a Form 4?

An open market or private purchase of the securities.

What does code M mean?

Exercise or conversion of a derivative, such as stock options.

What does code F mean?

Shares withheld or delivered to pay an exercise price or tax.

Is insider selling a bad sign?

Not necessarily; many sales are planned or for personal reasons.

What is a 10b5-1 plan on Form 4?

A pre-arranged trading plan; since April 2023 a checkbox shows trades made under one.