# What Is Insider Buying? Definition and Example

> What counts as insider buying, how it is reported on Form 4, and what research says about when it is a useful signal.

Source: https://www.exent.ai/learn/insider-buying · Reviewed by David, Senior Analyst, Exent · Published Oct 25, 2026 · Updated Oct 25, 2026

## Key takeaways

- Insider buying is when a company’s officers, directors or 10%+ owners buy its shares with their own money; it must be reported on SEC Form 4 within two business days.
- Research by Cohen, Malloy and Pomorski (2012) found that “opportunistic” insider trades predicted returns, while “routine” ones carried roughly no signal.
- Open-market buys say more than option exercises, grants or planned purchases.
- Several insiders buying at once (a cluster) is commonly read as a stronger signal than one buyer, but it is still not a guarantee.

## What is insider buying?

An insider is an officer, a director or an owner of more than 10% of a company’s shares. When one of them buys stock in the open market, it is insider buying. The SEC’s [Forms 3, 4 and 5 bulletin](https://www.sec.gov/files/forms-3-4-5.pdf) states that [Form 4](https://www.exent.ai/learn/form-4) must be filed within two business days of the trade, so these buys become public quickly, unlike a [13F](https://www.exent.ai/learn/13f-filing).

## Which insider trades matter?

| Transaction | What it usually signals |
| --- | --- |
| Open-market purchase | The most informative: the insider chose to put cash in |
| Several insiders buying in the same weeks | Read by many investors as a stronger signal |
| Option exercise or stock grant | Little: part of pay, not a market view |
| Routine purchase on a schedule | Little: happens every year regardless of outlook |

## Is insider buying a good signal?

Sometimes. In [“Decoding Inside Information” (Journal of Finance, 2012)](https://ideas.repec.org/a/bla/jfinan/v67y2012i3p1009-1043.html), Cohen, Malloy and Pomorski split insiders into routine traders, who trade in the same pattern each year, and opportunistic ones. A value-weighted portfolio of opportunistic trades earned about 82 basis points a month in abnormal returns in their sample; routine trades earned roughly zero. That is a historical, academic result before costs, not a trading rule.

Illustrative: a CFO who has never bought before spends $400,000 on shares after a 30% fall. That is a different message from a director whose purchase every March is a habit.

## How investors use it

Insider activity works best as one input next to fundamentals and analyst views. Selling is a weaker signal, because insiders sell for taxes, diversification and purchases (see [insider selling](https://www.exent.ai/learn/insider-selling)). More in [how to track smart money](https://www.exent.ai/resources/how-to-track-smart-money).

## Common mistakes

- Counting grants and option exercises as buys.
- Ignoring size: a purchase that is small next to the insider’s pay says little.
- Treating one buy as a reason on its own to own the stock.

## See insider buying with Exent

1. Open a stock in Stocks Radar to see insider, congress and 13F “smart money” activity.
2. Portfolio Analysis shows analyst and insider activity on the holdings you upload.

Exent is our product: [Exent Gems](https://www.exent.ai/radar)

## Frequently asked questions

### How quickly must insider buys be reported?

Within two business days of the trade, on SEC Form 4, according to the SEC. The filings are public on EDGAR.

### Is insider selling a bad sign?

Not necessarily. Insiders sell for many personal reasons, so selling is usually read as a weaker signal than buying.

### What is a cluster buy?

A cluster buy is when several insiders of the same company buy shares within a short period. Many investors treat it as stronger than a single purchase.

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Educational content, not investment advice. Past performance does not guarantee future results.