How bonuses are withheld
A bonus is “supplemental wages” for payroll. When it’s paid separately from your regular wages, or the amounts are shown separately on the same check, your employer can choose one of two methods for federal income tax:
- Flat rate: 22% of the bonus, no matter what your W-4 says. Supplemental pay above $1 million in the year is withheld at 37%.
- Aggregate method: the bonus is added to your regular wages for the period, withholding is figured on the total as if that were your normal pay, and the tax already withheld on the regular wages is subtracted. Because the formula annualizes that one big check, it often withholds more than 22%.
Social Security (6.2% up to the yearly wage base) and Medicare (1.45%, plus 0.9% above $200,000) apply to bonuses exactly like regular pay.
State tax on bonuses
Many states publish a flat supplemental rate for bonuses paid separately; others run the bonus through the regular withholding formula. The calculator uses your state’s own 2026 rule: pick your state to see it.
Withholding is not your final tax
Whatever is withheld, your bonus is taxed as ordinary income on your return together with the rest of your pay. If the bonus withholding was higher than the tax you owe, the difference comes back as part of your refund; if it was lower, you pay the rest when you file.