When a person or group of persons acquires beneficial ownership of more than 5% of a class of a company’s equity securities registered under Section 12 of the Securities Exchange Act of 1934, they must file a Schedule 13D with the SEC. The term "beneficial owner" is defined under SEC rules. It includes any person who directly or indirectly shares voting power or investment power (the power to sell the security).

Schedule 13D reports the acquisition and other information within ten days after the purchase. The schedule is filed with the SEC and is provided to the company that issued the securities and each exchange where the security is traded. Any material changes in the facts contained in the schedule require a prompt amendment. The schedule is often filed in connection with a tender offer.