What is insider buying and why does it matter?

Insider buying occurs when a company's executives, directors, or major shareholders purchase shares on the open market using their own money. It matters because insiders - people who know the business most intimately - are choosing to increase their exposure. Academic research consistently shows that stocks with high insider buying outperform the market over 6-12 month periods.

Is insider selling a bad sign?

Not necessarily. Insiders sell shares for many non-negative reasons: diversification, paying taxes, home purchases, retirement, or exercising expiring options. A single insider selling a small portion of their holdings is rarely meaningful. Concerning patterns include multiple insiders selling simultaneously, an insider liquidating the majority of their position, or selling during a period of apparent business stress.

Where can I find Form 4 filings?

All Form 4 filings are publicly available on SEC EDGAR (edgar.gov) within 2 business days of the transaction. You can search by company or individual. OpenInsider.com aggregates Form 4 data and makes it easy to filter.

How quickly must insiders report trades?

Insiders must file Form 4 within 2 business days of the transaction. This near-real-time reporting requirement means investors can see insider trades quickly after they occur. Late filing is a violation and the SEC does take enforcement action for habitual late filers.

What is a 10b5-1 plan?

A 10b5-1 plan is a pre-scheduled trading plan that allows insiders to sell shares on a predetermined schedule, insulating them from accusations of trading on inside information. If an insider sets up a 10b5-1 plan when they have no material non-public information, they can execute trades automatically even during blackout periods. Selling under a 10b5-1 plan is less informative as a bearish signal than unscheduled discretionary selling.

How to Track Insider Buying and Selling

Insiders - executives, directors, and major shareholders - must report their trades to the SEC within 2 business days. These disclosures, filed as Form 4, create a public record of when the people who know a business best are buying or selling with their own money. Tracking insider activity is one of the most reliable qualitative signals available to individual investors.

What is insider trading (the legal kind)?

In everyday language, “insider trading” connotes illegal activity - trading on material non-public information. But legal insider trading is simply transactions by corporate insiders (officers, directors, and 10%+ shareholders) who follow the disclosure rules. They must:

Report transactions on Form 4 within 2 business days
Not trade on material non-public information (MNPI), meaning significant information not yet shared with the public
Comply with company trading windows and blackout periods (times when insiders are prohibited from trading, typically around earnings announcements)

This guide covers only legal insider trading and what it reveals through public disclosures.

Why insider buying is a meaningful signal

When a CEO spends $2 million of their own money buying stock in the open market, that’s meaningful. Consider:

They know the business better than anyone, seeing revenue trends, customer pipelines, R&D progress, and competitive dynamics in real time. They’re using their own after-tax cash, not exercising a stock option grant, making it a voluntary decision to increase personal exposure. And they’re taking on concentration risk, since most insiders already have significant company exposure through their salary, options, and existing shareholdings.

Academic research by Seyhun, Lakonishok, and Lee consistently finds that stocks with high insider buying outperform those with insider selling over 6-12 month horizons. The effect is strongest for smaller companies where insiders have the most information advantage.

How to read a Form 4

A Form 4 contains the insider’s name and title (CEO, CFO, director, or 10%+ shareholder), the transaction date, a transaction code indicating the type of trade (see table below), the number of shares involved, the price per share, and the total shares owned after the transaction. That last field is especially useful because it puts the trade in context relative to the insider’s overall position.

Form 4 transaction codes

Code	Meaning	Investor significance
P	Open market purchase	Yes - Strong bullish signal
S	Open market sale	Mixed - Weak signal - many benign reasons
A	Grant/award (stock compensation)	Neutral - part of comp package
D	Disposition (return to issuer)	Neutral - usually related to comp
F	Tax withholding via share surrender	Neutral - covering tax on vest
M	Option exercise	Neutral - exercise of rights
G	Gift	Neutral - donation or personal transfer
J	Other	Varies

Focus on Code P (open market purchases), as these are the most meaningful. Code S sales are less informative due to the many non-bearish reasons for selling.

Patterns that matter vs. noise

Not all insider activity deserves the same attention. Here’s how to filter signal from noise:

High-signal patterns (worth investigating further)

Cluster buying is one of the strongest signals. When multiple insiders purchase shares within a short window (days or weeks), it’s worth paying attention. If the CEO, CFO, and three board members all buy simultaneously, they’re not coordinating - they’re all independently concluding the stock is undervalued.

Large dollar purchases also carry weight. An insider spending $500K to $5M+ in the open market is making a significant personal bet. Contrast that with token purchases of $10K-$50K that may be for appearances.

Buying near 52-week lows is particularly telling. Insiders buying during a sell-off signals they believe the decline is overdone and the business is worth more than the market thinks.

A new position by an activist director can also be meaningful. When a new board member (often an activist investor) buys a large stake shortly after joining, it signals they see significant value creation opportunity.

Low-signal or noisy patterns

Routine selling under 10b5-1 plans tells you very little. These are pre-scheduled plans set up in advance, so the fact that selling happens doesn’t reflect current insider sentiment.

Post-option-exercise selling is similarly uninformative. Immediately selling shares acquired through option exercise is common tax optimization, not bearish conviction.

Small dollar amounts are easy to over-interpret. A CFO buying $15,000 of stock in a company with a $500M market cap is not a meaningful signal.

A single seller with multiple possible reasons is also noise. One executive selling could be covering a down payment on a house, college tuition, or estate planning.

Where to find Form 4 data

SEC EDGAR

The primary source. All Form 4s are filed at edgar.gov. Search by company ticker or CIK number. Choose “4” under form type. Free but requires manual navigation.

EDGAR full-text search (efts.sec.gov) lets you search across all filings for specific insider names or companies.

OpenInsider

OpenInsider.com is a free aggregator specifically for Form 4 data. It offers pre-filtered screens for common searches like cluster buys and CEO purchases above $500K, along with historical insider transaction history by company and screeners by sector, market cap, and transaction size. No login is required.

Finviz

Finviz’s insider trades section (finviz.com/insidertrading.ashx) shows recent insider transactions with links to the EDGAR filing. The premium version adds historical data and filtering.

Direct EDGAR RSS feeds

EDGAR provides RSS feeds for any company’s filings. When any Form 4 is filed for a company you’re watching, you’ll see it in your feed reader. Free, but no filtering.

The 10b5-1 plan: what it means

A 10b5-1 plan is a written trading plan that an insider sets up in advance (typically 30-90+ days before any trades occur), specifying:

The number of shares to sell
The price or formula for selling
The dates of sales

Because the plan is established when the insider presumably doesn’t have MNPI, subsequent sales are insulated from insider trading allegations. The SEC strengthened 10b5-1 rules in 2023 to require cooling-off periods and limit same-day plan establishment and trading.

For investors: When you see “sale pursuant to 10b5-1 plan” on a Form 4, weight the selling signal much less. The decision to sell was made weeks or months ago. Conversely, discretionary selling (no plan cited) in large amounts is more concerning.

Putting it together

How you use insider data depends on what you’re trying to do.

Monitoring companies you already own

If you hold a stock, insider activity is a useful ongoing signal. Set up EDGAR RSS feeds or check OpenInsider periodically for your holdings. When an insider buys, that’s a data point confirming your thesis. When multiple insiders sell outside of 10b5-1 plans, it’s worth digging into the most recent 10-Q to understand whether something has changed. You’re not screening for ideas here, you’re looking for confirmation or contradiction of what you already believe about the business.

Screening for new investment ideas

Some investors use insider buying as a starting screen for finding undervalued companies. OpenInsider’s “cluster buys” filter is useful for this: look for multiple insiders buying within the same 30-day window, since independent decisions to buy by several people who know the business well is a stronger signal than any single purchase.

When a cluster buy catches your eye, check the dollar amounts relative to each insider’s compensation (a $1M purchase from someone earning $800K annually means more than the same amount from a $5M earner). Then look at the company’s recent performance. Buying after a sell-off or disappointing earnings is more informative than buying during a run-up. From there, read the most recent 10-K or 10-Q to understand the business context before deciding whether to research further.