SEC Form 4 is filed within 2 business days when a corporate insider transacts in their company's stock. It's the fastest public data on what executives are doing with their own money.
Most people read it wrong. Here's a practical guide.
What Form 4 covers
Form 4 must be filed by:
- Officers (CEO, CFO, COO, etc.)
- Directors (board members)
- 10%+ beneficial owners (major shareholders)
Within 2 business days of any transaction in the company's equity securities.
The transaction codes that matter
| Code | Transaction | Signal strength |
|---|---|---|
| P | Open-market purchase | Highest — insider buying with their own money |
| S | Open-market sale | Moderate — discretionary selling |
| M | Option exercise | Low — often routine compensation |
| F | Tax withholding | None — automatic, not a choice |
| G | Gift | None — estate/tax planning |
| J | Other (various) | Context-dependent |
The hierarchy
Code P (purchase) is the strongest signal. When an insider spends their own cash to buy shares at market price, they believe the stock is undervalued. This is the purest conviction signal in public markets.
Code S (sale) is meaningful but noisier. Insiders sell for many reasons beyond bearishness: diversification, buying a house, funding a startup, tax planning, divorce. You need context.
Code M (exercise) and Code F (tax withholding) are mostly noise. Options have expiration dates. RSUs vest on schedules. These transactions are planned, not reactive.
How to read a Form 4
Table I: Non-derivative securities
This shows direct stock transactions:
- Column 1: Date
- Column 2: Transaction type (the code letter)
- Column 3: Number of shares
- Column 4: Price per share
- Column 5: Shares owned after the transaction
Table II: Derivative securities
This shows options, warrants, and convertible securities:
- Exercise price
- Expiration date
- Underlying shares
Footnotes
Often the most important part:
- 10b5-1 plan disclosures (pre-scheduled trades)
- Trust/entity ownership details
- Transaction context
The signals that matter
Strongest bullish signal: Cluster buying
Multiple insiders (CEO + CFO + directors) all buying in open market within the same week. This is the closest thing to a consensus insider view.
Strong bullish signal: Large purchase relative to salary
A CFO earning $500K/year buying $2M in stock is putting 4 years of salary at risk. That's conviction.
Moderate bearish signal: CEO selling >50% of holdings
A CEO trimming 5% is noise. A CEO selling more than half their position deserves investigation.
Weak/no signal: Routine exercises and tax withholding
Code M and Code F transactions that coincide with vesting dates are payroll mechanics, not market views.
The 10b5-1 plan complication
Many insider sales happen under 10b5-1 plans — pre-scheduled trading programs set up months in advance. These plans are designed to insulate insiders from trading on material non-public information.
What this means: A sale under a 10b5-1 plan was decided months ago. The timing doesn't reflect current views.
What to watch: When an insider terminates a 10b5-1 plan and then doesn't sell. That's a bullish signal — they had planned to sell but changed their mind.
Dollar context matters
| Insider sale | Context | Signal |
|---|---|---|
| $100K sale, $50M holdings | 0.2% of position | Noise |
| $5M sale, $50M holdings | 10% of position | Worth investigating |
| $40M sale, $50M holdings | 80% of position | Strong signal |
| $100K purchase, $300K salary | 33% of annual comp | Strong conviction |
Timing patterns
Post-earnings buying
Insiders buying within days of an earnings release (after the blackout window opens) signals they liked what they saw in the numbers before the market fully digested them.
Pre-announcement selling
Insiders selling before bad news can be illegal (insider trading). The SEC watches this closely. When you see large sales followed by negative announcements, it may lead to enforcement action.
Consistent scheduled selling
Monthly or quarterly sales of fixed amounts are usually 10b5-1 plan executions. Ignore them for signal purposes.
The practical workflow
- Filter for Code P first — open-market purchases are the highest-signal transactions
- Check dollar amount vs. holdings — is the transaction meaningful relative to their total stake?
- Look for clusters — multiple insiders acting similarly is stronger than one
- Read the footnotes — 10b5-1 plans, trust structures, and context matter
- Cross-reference with price action — buying after a decline is more meaningful than buying at all-time highs
Originally published at 13F Insight
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