How to Read Form 4 Transaction Codes: P, S, M, G, A, F Explained

Why Transaction Codes Matter

Every Form 4 filing includes a transaction code — a single letter that describes what the insider actually did. If you read only the headline (“CEO sold 100,000 shares”) without checking the code, you will regularly misinterpret insider behavior. A sale (code S) and a tax withholding (code F) look identical in the share count, but they mean completely different things.

The Eight Codes You’ll See Most Often

Code	Name	What It Means	Signal Strength
P	Purchase	Open-market buy with personal funds	Strong bullish — voluntary capital deployment
S	Sale	Open-market sell for cash	Potentially bearish — but check context
M	Exercise/Conversion	Option exercise or derivative conversion	Neutral — routine compensation event
A	Award/Grant	Stock award from company compensation plan	Neutral — not a market transaction
F	Tax Withholding	Shares withheld to cover tax on award/exercise	Neutral — mandatory, not discretionary
G	Gift	Transfer to charity, trust, or family member	Neutral — no market impact, estate/philanthropy
C	Conversion	Class B → Class A share conversion	Neutral — restructuring, not selling
J	Other	Catch-all for transfers, forfeitures, adjustments	Varies — read the footnotes

The Common Misreads

"CEO sold 500,000 shares" — but the code is F

Tax withholding (code F) is mandatory. When an executive receives a stock award, the IRS requires tax payment. The company withholds shares equal to the tax bill and reports it as a Form 4 transaction. The executive had no choice. This is not selling conviction — it is payroll processing.

"Insider dumped shares" — but the code is G

A gift transaction (code G) means the insider transferred shares to a charity, trust, or family member. No shares hit the open market. No selling pressure was created. Jeff Bezos regularly gifts Amazon shares worth hundreds of millions — but none of those shares were sold on an exchange.

"Big insider buy" — but the code is A

An award (code A) is a stock grant from the company. The insider did not spend personal money to buy shares. It is compensation, not conviction. Only code P (open-market purchase) represents voluntary buying with personal capital.

The Signal Hierarchy

Not all transactions are equal. Here is how to rank them by information content:

P (Purchase): The strongest signal. The insider chose to spend personal money at market price. This is as close to “putting their money where their mouth is” as it gets.
S (Sale) with no preceding A or M: A discretionary sale unrelated to compensation. Check whether it is part of a 10b5-1 pre-planned trading plan.
M + S combination: Exercise options, then sell the resulting shares. Common, routine, and usually low-signal unless the timing is unusual.
A, F, G, C, J: Administrative transactions. Important for tracking ownership changes, but not indicative of market sentiment.

How to Check on 13F Insight

On any insider profile page, the transaction history shows each filing with its code, date, shares, price, and shares owned after. Use the code column to filter signal from noise.

Frequently Asked Questions

What is the most bullish Form 4 transaction code?

Code P (open-market purchase) — the insider voluntarily spent personal money to buy shares at market price. This is the strongest positive insider signal.

Does a Form 4 sale (code S) always mean the insider is bearish?

No. Many sales are pre-planned under 10b5-1 trading plans, or follow option exercises (M + S). Context matters — check the timing, the proportion of holdings sold, and whether the insider retains a large position.

What does transaction code F mean?

Code F is tax withholding — the company automatically withholds shares to cover the tax liability on a stock award. The insider has no discretion over this transaction.

How do I tell if an insider gift (code G) matters?

Gift transactions do not affect the stock price directly because no shares are sold on the open market. They matter for tracking the insider’s remaining ownership and for understanding their estate or charitable planning.