What Form 4 codes P, S, A, M and F actually mean

On a Form 4, the difference between an insider buying shares and an insider being handed shares comes down to one character in the transaction code column. A P means they went into the market and bought stock. An A means the company gave it to them. An M means they exercised a derivative they already held. The dollar figures can look identical and the events are not remotely the same.

The SEC publishes the full code list, and five codes cover most of what turns up in an insider feed: P, S, A, M and F. Learning those five is most of the work of reading Form 4 activity sensibly.

What the five codes mean

The SEC defines them plainly. P is an open market or private purchase of a non derivative or derivative security. S is an open market or private sale of one. A is a grant, award or other acquisition under Rule 16b-3(d). M is the exercise or conversion of a derivative security exempted under Rule 16b-3. F is the payment of an exercise price or tax liability by delivering or withholding securities incident to the receipt, exercise or vesting of a security.

Read those slowly and the split is obvious. Two of them, P and S, describe a decision to transact in the market. The other three describe compensation moving through its normal stages. The SEC's own list keeps them apart too: P and S sit under the general codes, while A, M and F sit under the Rule 16b-3 codes, which cover exempt transactions between an insider and the company.

P and S: the codes where the insider chose

A P is a purchase. The insider moved their own money into stock at a price they could see, on a day they picked, when doing nothing was available to them. That last part is what gives the code its weight. Nothing in an executive's contract requires them to buy shares, so a purchase is discretionary, and the price column on the line records what they were willing to pay. The reasoning behind treating that as the more informative event is set out in what insider buying means.

An S is the mirror image, a sale in the market. It is discretionary in form as well, although as the piece on what insider selling tells you sets out, there are plenty of ordinary reasons for a sale that have nothing to do with a view on the business.

A, M and F: compensation moving through its stages

An A is a grant or award. The company issued shares or units to the insider under a plan. They did not buy anything and usually paid nothing, which is why these lines so often show a price of zero. A grant tells you about the company's pay structure and its vesting calendar. It does not tell you what the recipient thinks of the stock, because they did not choose to receive it on that day.

An M is an exercise or conversion of a derivative the insider already held, and stock options are the usual case. The option leaves Table II of the form and ordinary shares arrive in Table I. The price shown against the M is the strike, not the market price. On its own an M line is close to an accounting event: the insider converted one form of exposure into another, often because the option was approaching expiry.

An F is the settlement mechanic. When shares vest or an option is exercised, tax is owed, and the common arrangement is for the company to withhold shares or take delivery of shares to cover the exercise price or the tax bill. That withholding is reported as a disposal with code F. It looks like the insider parted with stock, and they did, but not by choice and not into the market. The trigger was usually a vesting date set years earlier.

The exercise and sell, and why it reads bigger than it is

The pattern that confuses readers most is an M followed immediately by an S, often on the same day and in the same filing.

What happened is that the insider exercised options and then sold shares, either enough to cover the strike price and the tax or the whole parcel. The S line can carry a large share count at a real market price, so anything scanning only for disposals will flag it as heavy selling. Set against the M line directly above it, the picture is usually more mundane: an option with a finite life, exercised and turned into cash.

It is still a disposal. The insider could have held the shares instead of selling them, and choosing not to is information of a sort. The honest reading is that an M and S pair carries less weight than a bare S of similar size, not that it carries none. Either way, the code column is what tells you which one you are looking at, and checking it takes a few seconds.

Read the price column alongside the code

The price column is the quickest cross check. A P with a real price means market money. An A with a zero, or an M at a strike set years ago, means shares arrived through a plan. An F priced at the day's close means tax, not a decision.

Column 5 of Table I, the amount held after the transaction, is the other half of the check. An insider who exercises options and sells the resulting shares often finishes with the same holding they started with. An insider who buys with a P finishes with more than they had. The movement in that running balance is what separates a genuine increase in exposure from shares simply passing through, and it is one of the reasons it pays to read the whole form rather than the headline figure.

How InsiderPulse handles this

InsiderPulse reads the transaction code on every Form 4 it processes rather than treating all acquisitions and all disposals alike, so a P is not filed next to an A, and an F is not counted as a decision to sell. Those filings feed the 0 to 100 score each covered asset carries, alongside congressional trade disclosures, options activity, dark pool and volume data, prices and news. Insiders To Follow shows a person's filings in sequence, which is where a run of purchases stands apart from a vesting schedule. Ask Pulsey will explain a specific code on a specific filing and cite the filing it came from.

InsiderPulse is a data tool. Nothing on this page is financial advice.