Form 4 Filings: How to Read Insider Buying Without Fooling Yourself

Corporate insiders — officers, directors, and holders of more than 10% of a company's stock — have to report their trades to the SEC on Form 4 within two business days. It is one of the few genuinely fast disclosure regimes in the market, and unlike 13F filings with their 45-day lag, the information arrives while it still matters.

The catch is that most Form 4 filings are meaningless, and telling the meaningful ones apart takes a few specific filters.

The Only Signal That Reliably Works

Insiders sell for a hundred reasons: diversification, a house, tuition, a divorce, a scheduled plan set up eighteen months ago. Selling tells you almost nothing about the company.

Insiders buy for one reason. They think the stock is worth more than it costs. Open-market purchases — where an executive writes a personal check at the current market price — are the filing type worth paying attention to, and they are far rarer than sales.

This asymmetry is the foundation of every insider-tracking strategy that has held up in research. Buying carries information. Selling mostly does not.

Reading the Transaction Codes

Form 4 uses a code that tells you what actually happened, and skipping it is how people misread the data completely.

Code P — open market purchase. The one that matters. Real money, real conviction.

Code S — open market sale. Weak signal on its own. Check whether it was under a 10b5-1 plan before drawing any conclusion.

Code A — grant or award. Compensation, not a decision. An executive receiving 40,000 restricted shares did not buy anything.

Code M — option exercise. Often followed immediately by an S. This is converting compensation to cash, not a view on valuation.

Code F — shares withheld for taxes. Purely administrative. It shows up as a disposition and means nothing.

A headline reading "insiders dumped $40 million in shares" is frequently describing codes M, S, and F on the same set of option exercises. The transaction code is what separates a real signal from a payroll event.

The 10b5-1 Distinction

Rule 10b5-1 lets insiders set up automatic trading plans in advance. Once the plan is running, trades execute on a schedule regardless of what the insider knows or thinks at the time. Form 4 filings indicate when a transaction was made under one of these plans.

A scheduled 10b5-1 sale carries no information. A discretionary open-market sale, made by choice, carries slightly more — though still much less than a purchase.

Purchases under a 10b5-1 plan exist but are uncommon. The overwhelming majority of insider buying is discretionary, which is part of why it is the more informative side.

What Makes a Purchase Worth Acting On

Size relative to the insider's compensation. A CEO earning $12 million buying $50,000 of stock is a gesture. The same CEO buying $3 million is a statement. Scale the dollar figure against what that person makes.

Cluster buying. One director buying is one opinion. The CFO, two directors, and the COO all buying inside the same two weeks is the strongest configuration in the entire dataset. Clusters have consistently outperformed isolated purchases in academic work on the subject.

Who is buying. The CFO has the clearest view of the numbers. The CEO has the clearest view of the strategy. An independent director who joined the board last quarter has neither. Weight accordingly.

Buying into weakness. An insider purchasing after a 35% drawdown is a different signal than one buying at all-time highs. The first suggests the decline is viewed internally as mispricing.

What It Cannot Tell You

Insiders are wrong regularly. They are overconfident about their own companies as a group, and plenty of executives have bought aggressively on the way to zero. The signal is a probability tilt, not a verdict.

The timing is also imprecise. Insider purchases tend to lead performance over six to twelve months in the research, not over the next two weeks. Buying calls expiring in 30 days off a Form 4 is using a long-horizon signal to justify a short-horizon instrument, and the mismatch is where the strategy usually fails in practice.

Combining It With Flow

Form 4 data becomes more interesting alongside options positioning. An insider cluster buy in a name that is simultaneously seeing unusual call activity and elevated block volume suggests multiple independent parties reaching the same conclusion at the same time.

That convergence is much rarer than either signal alone, and it is the configuration worth building a watchlist around. TraderDaddy Pro tracks insider activity with the transaction codes intact, and the live flow feedshows whether the options market is agreeing with them.