What is an I-9 and why does it need to be verified?

Form I-9 is a legal document that an employer uses to confirm that a person is eligible to work in the United States. The U.S. Citizenship and Immigration Services Department (USCIS) prohibits employers from hiring and employing individuals not authorized to work in the United States. Therefore, employees must prove they are eligible to work in the U.S. by presenting documented proof of eligibility, and employers must verify that those documents were presented and that the documents seem legit.