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.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. A state W-4 Form is a tax document that serves as a guide for employers to withhold a specific amount on each paycheck to go towards state taxes. Taxpayers can complete transactions on MyTax DC or call 202-727-4TAX. This form explains how much money to withhold for federal income taxes. Note that employees can fill out a new Form W-4 when applicable. Every employer who maintains an office or transacts business in Iowa and who is required to withhold federal income tax on any compensation paid to employees. Desarrollo, Washington.