Summary tables are a good place to discover insider trades, but they should not be the final word on any trade that matters to you. The authoritative record is the original Form 4 filed on EDGAR, the disclosure system run by the U.S. Securities and Exchange Commission. Checking the source takes a few minutes, confirms the numbers you are relying on, and often changes the interpretation once you read the footnotes. This habit separates careful readers of insider data from people who trade on a possibly mistaken row in a database.
Start at the EDGAR company search and enter the company name or ticker. Filter the results to Form 4, or browse the company filing index and look for the filing dated shortly after the trade you saw. Form 4 is generally due within two business days of the transaction, so the filing date should be close to the transaction date. Open the filing detail page and choose the main document, which is usually an XML based form rendered as a readable ownership report. You can also search EDGAR by the insider name, which is useful when a director serves on several boards and files for more than one company in the same week.
Once the document is open, verify the basics one by one. Confirm the reporting person name and relationship to the issuer: officer, director, ten percent owner, or a combination. Confirm the transaction date, not just the filing date. In Table I, for non-derivative securities, check the transaction code, the number of shares acquired or disposed of, and whether the code is A for acquired or D for disposed of. Check the price per share, and note if it is shown as zero, which usually means a grant, gift, or other non market event rather than a purchase. Then check the column that matters most for context: the amount of securities beneficially owned after the transaction. A purchase of 1,000 shares means one thing if the insider now holds 2,000 shares and something else if they now hold 200,000.
In Table II, for derivative securities such as options, check the exercise price, expiration date, and the underlying shares. An option exercise followed by an immediate sale of the underlying shares is a very different event from an exercise where the insider keeps the shares and pays the exercise cost and taxes in cash.
Next, read every footnote attached to the rows you care about. Footnotes explain weighted average prices and the range behind them, identify shares held indirectly through a spouse, trust, partnership, or retirement plan, and disclose trades made under a Rule 10b5-1 plan. They also explain share withholding for taxes, vesting schedules for awards, and disclaimers of beneficial ownership. The remarks section near the end sometimes adds context that does not fit in the tables. Skipping this section is how readers mistake a tax withholding disposal for an open market sale, or a grant for a confident purchase.
Aggregators process thousands of filings automatically, and errors do occur. Common ones include grants coded as buys, option exercises shown without the related sale, duplicate rows when an amendment is filed, indirect holdings counted twice, and prices carried over from the wrong row. Amendments are filed on Form 4/A, and if you see one, it replaces the original for the corrected items. When a summary number looks surprising, such as a purchase larger than the insider total holdings or a sale at a price far from the market that day, the original filing usually resolves it in a minute. Keep a simple note of what you verified: date, code, shares, price, holdings after, and any plan or footnote that changes the meaning.
Doing this for every row would be slow, and it is not necessary. Do it for any trade you might act on, any trade that is unusually large, and any trade that a headline or social media post is presenting as a strong signal. The source is free and public for exactly this reason.
Nothing here is investment advice. It is a guide to checking a public document so your own research rests on accurate facts.