Form 4 Transaction Codes: P, S, A, M, F and More Explained

A Form 4 line can report many different kinds of events, and the only thing that tells you which one happened is a single letter, sometimes two, in the transaction code column. Reading the code correctly is the difference between seeing a deliberate purchase and mistaking an option exercise or a tax withholding event for one. This guide lists every official Form 4 transaction code and groups them by what they actually represent.

Where the codes come from

The SEC's General Instructions to Form 4 define a fixed set of transaction codes, grouped into a few categories: general market transactions, transactions exempt under Rule 16b-3, derivative security transactions, other exempt and small acquisition transactions, and a handful of other codes for less common events. Every filer uses the same codes, which is what makes the data comparable across companies.

General transaction codes

These are the codes most people mean when they talk about insider buying or selling. A P or S reflects an actual purchase or sale decision made at or near the transaction date, rather than a mechanical event tied to compensation.

Codes exempt under Rule 16b-3

Rule 16b-3 exempts certain transactions between an insider and the issuer from the short swing profit rules of Section 16(b), as long as they meet specific conditions, typically approval by the board or a committee of non-employee directors.

Derivative security codes

These codes cover transactions in derivative securities, such as stock options, that are not otherwise exempt under Rule 16b-3.

Codes E and H appear less often than the others, since most options are either exercised before expiration or simply lapse worthless, which is reported as an expiration rather than a sale.

Other exempt and small acquisition codes

A code G transaction, for example, tells you that shares changed hands as a gift rather than at a market price, which is why the reported price per share is often zero or blank.

Other transaction codes

Code J is a catch-all, so whenever you see it, check the filing's footnotes for the actual description rather than relying on the code alone.

Reading codes together with the rest of the row

The code only tells you the category of event. To understand a specific transaction, read it alongside:

• Price. A nonzero price next to codes P, S, M or X tells you money changed hands. Codes A, F, G and W often show no price or a nominal one.
• Shares owned after the transaction. This shows the resulting position, which matters more than any single transaction in isolation.
• Ownership type. D for direct or I for indirect, for example through a trust, a spouse's account or an LLC.
• The Rule 10b5-1 flag. Since 2023, a Form 4 marks whether a P or S transaction was made under a prearranged trading plan adopted in advance.

Working with transaction codes in code

SecFeed extracts the transaction code into its own field on every insider trading row, so you can filter without parsing the filing yourself. To see only open market purchases above a threshold:

curl "https://secfeedapi.com/v1/insider-trading?code=P&minValue=100000&size=25" \
  -H "Authorization: Bearer YOUR_API_KEY"

To compare how often different codes occur for one company, pull a broader set and group by code in Python:

from secfeed import Client
from collections import Counter

sf = Client("YOUR_API_KEY")
rows = sf.insider_trades(ticker="NVDA")
counts = Counter(r["code"] for r in rows)
print(counts)

The table parameter on the same endpoint lets you separate non-derivative transactions, mostly common stock, from derivative transactions, mostly options, if you want to analyze each table independently. See the full parameter list at the insider trading endpoint, and the surrounding form structure in SEC Form 4 Explained.

Frequently asked questions

What is the most common Form 4 transaction code?

Across most companies, codes A, F, M, P and S account for the large majority of filings, since they cover ordinary equity compensation grants, exercises, tax withholding and open market trades.

Does code S always mean an insider is bearish?

No. An open market sale can be driven by diversification, taxes, a planned expense or a prearranged Rule 10b5-1 plan set up months in advance. The code identifies the type of transaction, not the reason behind it.

Why do some Form 4 rows show no price?

Transactions like gifts (code G), inheritance (code W) and some grants (code A) do not involve a market price, so the price field is often zero or left blank on those lines.

Is there a code for stock buybacks by the company itself?

No. Form 4 reports transactions by individual insiders under Section 16, not company level buyback programs, which are disclosed separately, such as in periodic reports.

Where can I find the official list of codes?

The complete, authoritative list is published in the General Instructions to Form 4 on sec.gov. SecFeed extracts the same codes directly from each filing's data.