Complete Form W-4 so that your employer can withhold the correct federal income tax from your pay. Give Form W-4 to your employer.Information about Form W4, Employee's Withholding Certificate, including recent updates, related forms and instructions on how to file. Withholding Tax Forms for 2017 Filing Season (Tax Year 2016) (Please note the Office of Tax and Revenue is no longer producing and mailing booklets. Employees who work in a locality with state income tax must fill out a withholding form. Learn which state W-4 form your employees must use. Employees will be able to understand the tax terms used and read multiple long publications just to fill out a W4 for estimated withholding. Caution: If you don't return Form W-9 to the requester with a TIN, you might be subject to backup withholding. See What is backup withholding, later. It's critical for successful reporting to use the correct format and color of ink.