Purpose. Complete Form W-4 so that your employer can withhold the correct federal income tax from your pay. Consider completing a new Form W-4 each year.The Tax Department is streamlining withholding tax and wage reporting forms and Web File applications. Tax Withholding Forms and Instructions. Federal Withholding Certificate (W-4). Information about Form W4, Employee's Withholding Certificate, including recent updates, related forms and instructions on how to file. Will the employer provide me with w4 form or do I have to fill it out on IRS before the first paycheck? Documents that Establish Both Identity and Employment Authorization. The documents on List A show both identity and employment authorization. Complete Form W-4 so that your employer can withhold the correct federal income tax from your pay.