Employers are required to document the employment eligibility of their new hires by keeping on file the I-9 Employment Eligibility Verification Form. This requirement is enforced by the United States Citizenship and Immigration Services (USCIS), a division of the Department of Homeland Security. The form specifically requires employers to not only check the identity of their employees but to also verify documentation of their employees' authorizations to engage in permanent employment in the United States. The Form was last revised February 2, 2009 in order to reflect changes made to the rules on which documents employees may present to employers for the purpose of filling out the Form. One of the major changes to the I-9 documentation requirements is in the requirement to present only unexpired documents. Previously it was allowable for an employee to present an expired U.S. Passport as evidence of U.S. work authorization and of identity. The I-9 Form is not filed with U.S. Immigrations and Customs Enforcement (ICE) or with USCIS, but is kept on file by the employer in such as way as to be accessible for an inspection by authorized government officials. Employers are required to retain Form I-9 for a period of three years from the date of hire of a new employee or for one year following the employee's termination, whichever is later.