A periodic form filed with the SEC, the issuer, and the issuer’s stock exchange when there has been a nonexempt change in an insider’s ownership of company stock, such as a purchase, sale, or option exercise, and certain types of NQDC plans. The maximum period that may elapse between the transaction and the filing of Form 4 was shortened (from 10 days after the start of the following month) by the Sarbanes-Oxley Act. Now Form 4 must be filed before the end of the second business day after the day on which the relevant transaction took place. Compare to Form 3 and Form 5.
For details about these filings in the context of NQDC plans, see the related FAQ.