Form 4

A document that must be filed with the Securities and Exchange Commission (SEC) whenever there is a material change in the holdings of company insiders (including shareholders owning 10% or more of the company's outstanding stock).

Investopedia Says:

SEC regulations require insiders to report any material changes in their holdings of their affiliated company, via the submission of a Form 4, before the tenth day of the month following the material transactions. This covers buy and sell orders on the open market as well as the exercise of company stock options.

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Document, filed with the Securities and Exchange Commission and the pertinent stock exchange, which is used to report changes in the holdings of (1) those who own at least 10% of a corporation's outstanding stock and (2) directors and officers, even if they own no stock. When there has been a major change in ownership, Form 4 must be filed within ten days of the end of the month in which the change took place. Form 4 filings must be constantly updated during a takeover attempt of a company when the acquirer buys more than 10% of the outstanding shares.