Bonus paycheck tax calculator explained

Last updated: 2026-08-14

Bonuses, commissions, and some other payments are often treated as supplemental wages for withholding. That can make a bonus paycheck look heavily taxed even though final tax is reconciled on the annual return.

Flat vs aggregate withholding

A flat method applies a supplemental withholding rate to the bonus. An aggregate method combines regular wages and supplemental wages for the period, calculates withholding on the combined amount, and subtracts withholding already tied to regular pay.

Payroll taxes still matter

Social Security and Medicare can also apply to bonus wages, subject to the usual wage-base and additional Medicare rules. State and local handling depends on coverage and payroll settings.

Use the calculator

Use the bonus paycheck calculator to compare supplemental wage methods. For regular wages, start with the U.S. paycheck calculator.