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.Before making any entries, see the Note below, and if applicable, complete the worksheet in the instructions. Complete Form W4 so that your employer can withhold the correct federal income tax from your pay. Consider completing a new Form W-4 each year. To download a State W-4 Form with instructions, click here. This video goes over how to fill out a 2021 Form W-4 if you are single and the basics behind Form W-4. How to fill out tax form W4 Employee Withholding Certificate.