US Internal Revenue Code Section 3402 Income Tax Withholding at Source (26 USC 3402)

Section 3402 of the Internal Revenue Code, the source of every United States employer's duty to withhold federal income tax from wages: the requirement to withhold under the Treasury's tables, the percentage and wage bracket methods and the alternative methods, the half-period rule for mixed wages, the withholding allowance certificate (Form W-4) with its furnishing, ten-day change, thirty-day effect and lock-in mechanics, marital status, additional allowances for deductions and credits, the exempt-employee certificate, withholding on tips and on non-cash commissions, annuities and sick pay on request, voluntary withholding on federal payments and unemployment compensation, gambling winnings and tribal casino distributions, and the vehicle fringe benefit election. It comprises 16 controls organised across 3 domains, and applies in the United States.