Tax withholding in the United States
（重定向自Federal income tax withholding）
Three key types of withholding tax are imposed at various levels in the United States:
The amount of tax withheld is based on the amount of payment subject to tax. Withholding of tax on wages includes income tax, social security and medicare, and a few taxes in some states. Certain minimum amounts of wage income are not subject to income tax withholding. Wage withholding is based on wages actually paid and employee declarations on Federal and state Forms W-4. Social Security tax withholding terminates when payments from one employer exceed the maximum wage base during the year.