330 ILCS 56/20

A private employer who maintains a veterans' preference employment policy pursuant to Section 15 of this Act may require and rely on an applicant's or employee's Department of Defense DD214/DD215 forms or their predecessor or successor forms, an applicant's or employee's NGB-22 discharge form or its predecessor or successor forms (if a member of the National Guard), and a U.S. Department of Veterans Affairs award letter (if the applicant or employee is claiming a service-connected disability) to establish eligibility for such policy.