Form 4
Also called insider transaction report.
The form company insiders use to report their trades in the company's stock, generally within two business days.
Officers, directors and owners of more than 10 percent of a class of the company's stock report their transactions in it on Form 4, generally within two business days. Source 1
Form 3 reports an insider's holdings when they first become an insider, and Form 5 covers certain transactions after the fiscal year ends. Source 1