Understanding SEC insider filings: Forms 3, 4, 5 and 144
Learn what insider filings tell you about ownership, transactions and proposed sales, and how to read the codes and footnotes behind the numbers.
By Chad Mazzola
An executive reports a change in their company shares. Did they buy more stock? Sell some? Receive an award, exercise options, or use shares to pay a tax bill?
Insider filings can tell you, but you need to know what you’re reading. The form, transaction code, and footnotes explain what happened. The number of shares alone doesn’t.
This introduction covers Forms 3, 4, 5 and 144: who files them, what each reports, and how to make sense of a disclosure.
Who files insider reports?
Forms 3, 4 and 5 generally cover company directors, certain officers, and beneficial owners of more than 10% of a covered class of equity securities. A reporting owner can be a person or an entity.
Two names matter when you open a filing: the issuer is the company whose securities are being reported, and the reporting owner is the person or entity disclosing their ownership. The issuer’s name on the form doesn’t mean the company itself bought or sold the shares.
These are routine public disclosures. Calling someone an insider here describes their reporting status; it doesn’t imply illegal trading.
What Forms 3, 4, 5 and 144 report
The forms answer different questions:
| Form | What it tells you |
|---|---|
| 3 | What the reporting owner holds when they first become subject to insider reporting |
| 4 | A change in ownership, including trades, awards, option exercises and other events |
| 5 | Certain transactions eligible for later reporting, or transactions that should have been reported earlier |
| 144 | A proposed sale under Rule 144, rather than confirmation that the proposed sale occurred |
A Form 3 establishes initial holdings. It doesn’t mean those securities were just purchased. Form 4 is where you’ll usually find subsequent transactions. Form 5 is required only in particular circumstances, so you shouldn’t expect one from every insider each year.
Form 144 follows a separate set of rules from Forms 3, 4 and 5. It’s useful alongside them, but it serves a different purpose.
How to read a Form 4
Start with the transaction code. It identifies the kind of event reported on each row. These are a few you’ll often encounter:
| Code | Meaning |
|---|---|
| P | A purchase in the market or through a private transaction |
| S | A sale in the market or through a private transaction |
| A | A grant, award, or certain other acquisitions under the relevant compensation rules |
| M | An exercise or conversion of a derivative, such as an employee stock option |
| F | Securities used to cover an exercise price or tax obligation |
| G | A gift |
P and S include private transactions as well as market trades. Awards and option exercises can also add shares to an account, but tell you something different from a purchase.
A separate acquired/disposed column tells you whether securities were added or removed. Its A and D flags are separate from the transaction codes. Read both columns together.
A real example: an award and tax withholding
In this Black Stone Minerals Form 4, officer Luke Putman reported two transactions dated 24 February 2026:
- 68,853 common units acquired, with transaction code A
- 25,302 common units disposed of, with transaction code F and a reported price of $15.23 per unit
The footnote explains that the transactions relate to a performance-unit award and tax withholding. Together, the codes and explanation show an award followed by units used to cover taxes. Reading the second row as a market sale would misdescribe what happened.
A single filing can also report an option exercise followed by a sale of the resulting shares. Those rows describe related steps; adding them together as separate purchases and sales can give a misleading picture.
What Form 144 tells you about a proposed sale
Form 144 gives notice of an intended sale of restricted or control securities under Rule 144. Restricted securities generally come from an unregistered transaction; control securities are held by an affiliate, such as someone with control over the company. These categories can overlap.
The notice can identify the seller, broker, number of securities proposed for sale, estimated market value, and approximate sale date. The SEC’s Form 144 explanation describes when a notice is required.
Treat those figures as proposed terms. The notice alone doesn’t confirm that the seller completed the sale, sold the full amount, or received the stated market value. It also contains separate information about how securities were acquired and sales during the previous three months. Those past sales aren’t the newly proposed sale.
Where a seller also has Form 4 reporting obligations, a later Form 4 may provide evidence of an actual sale. Compare the person, security, dates, and quantities rather than assuming the two filings match automatically.
Dates, ownership and footnotes matter
Check the transaction date as well as the filing date. Form 4 is generally due within two business days, so a filing published today may describe an earlier event. Form 5 can report much older transactions. A Form 144’s approximate sale date describes the proposal.
Distinguish shares from options. The ownership forms separate non-derivative securities, such as common shares, from derivatives, such as options that give the holder a right to buy shares. An option holding and its underlying shares aren’t interchangeable positions.
Look at direct and indirect ownership. Securities can be held in someone’s own account or indirectly through arrangements such as a trust or another entity. The ownership column and its explanation help you understand whose position is being disclosed.
Read the footnotes and remarks. They can explain tax withholding, price ranges, ownership arrangements, or a prearranged trading plan. Amendments, identified by /A after the form number, may correct an earlier disclosure; read them with the original.
Using insider filings in your application
Keep holdings, reported transactions, and proposed sales distinct. Then use the codes, dates, ownership details, and footnotes to explain each disclosure. That gives your users a much clearer account than labeling every increase a buy and every decrease a sell.
Chadwin provides structured ownership filings, transaction history, and proposed-sale notices through its API. See the insider filings guide for the available data and endpoints.