Form I-9 - Employment Eligibility Verification - Department of Homeland Security, U.S. Citizenship and Immigration Services: 
http://www.uscis.gov/files/form/i-9.pdf    New employees are required to complete Section 1 of page 4

W-4 - Employee's Withholding Allowance Certificate - Department of the Treasury, Internal Revenue Service: 
2021 W4 Form
New employees and any employee wanting to make a change in their federal income tax withholding.  SAU #93 requires the bottom portion of page 1 to be completed and on file.