How to Read a Form 4
A FilingRadar Editorial guide · · Sourced from sec.gov
What a Form 4 actually is
Form 4 is the filing every officer, director, and 10%-or-greater beneficial owner of a US public company must submit within 2 business days of any change in their beneficial ownership. The form discloses transaction type via a single letter code, share count, price, resulting position, and whether the trade was made under a 10b5-1 plan.
Section 16 of the Exchange Act mandates Form 4 (along with Form 3 for initial holdings and Form 5 for annual cleanup). The same section also forbids short-swing profits and short sales of company stock — see our Section 16 glossary entry for the mechanics.
The transaction code is the headline
Every Form 4 line item carries a single-letter transaction code that tells you what actually happened. Same insider, same dollar amount, different code = completely different signal. Below is the full SEC taxonomy as of 2026.
| Code | What it means | Signal |
|---|---|---|
| P | Open-market purchase | HIGH |
| S | Open-market sale | MED |
| A | Grant or award under employee plan | LOW |
| M | Option exercise (acquisition) | LOW |
| F | Tax-withholding share surrender | LOW |
| G | Gift (donor or recipient) | LOW |
| I | Disposition pursuant to a tender offer | MED |
| D | Disposition to the issuer (buyback participation) | MED |
| V | Voluntary reporting (transaction not otherwise reportable) | LOW |
| X | Exercise of in-the-money / out-of-money derivative | LOW |
| C | Conversion of derivative security | LOW |
| J | Other (filer should describe) | MED |
Signal rating is our editorial assessment of typical retail-investor information value, not a recommendation.
Why P-coded purchases are gold
Open-market purchases (code P) are the most informative single insider data point. Three reasons:
- Insiders rarely buy. Most insider compensation arrives as equity grants (code A) or option exercises (code M). Spending personal cash to buy more is unusual by design.
- Section 16 short-swing rules cost real money. Any profit from buying and selling within 6 months must be disgorged to the company. A purchase commits the insider to at least 6 months of exposure.
- Legal liability for trading on information is high. Selective insider buying ahead of good news is illegal trading; the legal-defense moat encourages caution.
The strongest variant: multiple insiders buying within the same 30-day window. Cluster buying is the closest thing in public markets to a free signal — academic studies consistently find excess returns over the 6-12 months following insider cluster buys.
Why S-coded sales are noisier than P-coded buys
Insiders sell for many non-informational reasons:
- 10b5-1 plans — pre-scheduled, automated
- Tax withholding on vesting (often shows up as code F instead of S)
- Diversification — sensible after a stock-price run
- Estate or charitable planning — code G for gifts
Always check the 10b5-1 checkbox added by the 2022 SEC amendments. A checked 10b5-1 box means the trade was set up months in advance and not based on the insider's view of current events; treat it as low-signal. A discretionary (non-10b5-1) sale by a CEO who never sells is far more informative than a scheduled monthly disposition.
See our entry on 10b5-1 plans for the cooling-off rules.
Reading a Form 4 in 60 seconds
- 10 sec — Note the filer: officer, director, or 10%-owner. CEO/CFO buys are higher signal than independent director buys.
- 10 sec — Check the transaction code. P, S, A, M are 90% of what you will see.
- 10 sec — Check the 10b5-1 checkbox. If checked, severely discount.
- 15 sec— Note the size relative to the insider's total holdings (also disclosed on the form). A CEO selling 5% of their stake is different from selling 50%.
- 15 sec — Cross-reference with recent Form 4 filings from the same company. Cluster patterns matter more than single transactions.
Form 4 red flags
- Cluster of S-coded sales by multiple officers within days of each other, no 10b5-1 plan. Coordinated insider exit patterns historically precede negative news.
- New 10b5-1 plan set up just before a quiet period or major announcement. The 2022 cooling-off period was added because abuses had become routine.
- Large gift transactions (code G) to family trusts. Sometimes legitimate estate planning, sometimes a way to dispose without triggering S-code disclosure.
- Repeated Form 5 corrections from the same insider. Routine carelessness, or systematic late disclosure?
- Officer suddenly stops filing. Could indicate the person is no longer a Section 16 reporting officer — check for a corresponding 8-K Item 5.02.
Frequently asked questions
What is a Form 4?
Form 4 is the SEC filing every corporate officer, director, and 10%-or-greater beneficial owner must submit within 2 business days of any change in their ownership of company stock. It reports the transaction type using SEC transaction codes (P, S, M, F, G), share count, price, and resulting position.
What does code P mean on a Form 4?
Code P means an open-market purchase — the insider used their own money to buy company stock on the open market. P-coded purchases are historically the most informative insider signal because they are rare and signal conviction.
What does code S mean on a Form 4?
Code S means an open-market sale. S-coded sales are noisier than P-coded purchases because executives often sell for non-informational reasons: scheduled 10b5-1 plans, tax withholding, diversification, or estate planning. Always check whether a 10b5-1 plan was disclosed.
How do I know if a Form 4 sale is from a 10b5-1 plan?
Since the 2022 SEC amendments, Form 4 has a checkbox flag indicating whether the reported transaction was made under a Rule 10b5-1 trading plan. A checked 10b5-1 box means the trade was pre-scheduled and not based on current information — treat it as low-signal compared to discretionary trades.
Related glossary terms
Ready to download a real 10-K?
FilingRadar lets you pull any 10-K as a clean PDF — free, no signup.