An SEC Form 4— formally a "Statement of Changes in Beneficial Ownership" — is the filing a corporate insider must submit to the U.S. Securities and Exchange Commission whenever they buy, sell, or otherwise change their holdings in their own company's stock. It is filed electronically through the SEC's EDGAR system and becomes public almost immediately, which is why Form 4 data is one of the most closely watched signals in the market.
Who must file, and how fast
Three categories of people are "insiders" for this purpose: company officers (like the CEO or CFO), directors on the board, and any beneficial owner of more than 10%of a class of the company's equity. When any of them transacts in the company's securities, a Form 4 must be filed within two business days. That short window is what makes the data actionable — you frequently see an insider's trade within days of it occurring.
What a Form 4 tells you
Each Form 4 lists one or more transactions with the date, the type of security, the number of shares, the price, whether shares were acquired or disposed, and the insider's total holdings after the transaction. A short letter transaction code describes exactly what happened — an open-market purchase (P), an open-market sale (S), an option exercise (M), a grant or award (A), shares withheld for taxes (F), and so on.
Why investors watch Form 4 activity
The logic is simple: nobody knows a company better than the people running it. When an executive spends their own money buying shares on the open market, it can signal confidence; when many insiders buy around the same time — a cluster buy — the signal is stronger still. Sales are noisier, because insiders sell for many routine reasons. Reading Form 4 activity well means separating meaningful open-market purchases from mechanical events like scheduled sales and tax withholding.
Frequently asked questions
How quickly must a Form 4 be filed?
Within two business days of the transaction. This tight deadline is what makes Form 4 data timely — you often see an insider's trade within days of it happening.
Who has to file a Form 4?
Corporate insiders: officers, directors, and beneficial owners of more than 10% of a company's equity securities. When any of them buys or sells the company's stock, a Form 4 is required.
Does a Form 4 sale mean the insider is bearish?
Not necessarily. Sales happen for many reasons unrelated to a view on the stock — taxes, diversification, or pre-scheduled 10b5-1 plans. Open-market purchases are generally considered a stronger signal than sales.
Continue: How to read insider trades · What are cluster buys? · Browse all tracked insiders.