New Hire Forms W-4 This form is used to determine employee's federal income tax withholding.  All of the forms on this page requires Adobe PDF Reader.  If you do not have it, you may download it here. IL W-4 This form is used to determine the correct amount of Illinois income tax withholding. I-9 All employees must complete this form at the time of hire for the Department of Homeland Security, U.S. Citizenship and Immigration Services.