Bonus tax calculator
The IRS treats bonuses, commissions, and severance as "supplemental wages" and gives employers two approved ways to withhold federal tax on them: the percentage method (a flat 22%, or 37% on the portion of a given employee's supplemental wages that exceed $1 million in the year) or the aggregate method (the bonus is combined with a regular paycheck and taxed at your annualized marginal rate). This calculator computes both, plus Social Security, Medicare, and a state-tax estimate, so you can see what a bonus check actually pays out under either method.
Withholding is not the same as your final tax liability. If your real marginal bracket is below the withholding rate applied, the difference typically comes back as part of your refund; if it's higher, you'll owe more at filing time.
Every calculation runs locally in your browser. Nothing you enter is uploaded or stored.
Sources & methodology
- Publication 15 (Circular E), Employer's Tax Guide (IRS.gov): Defines the 22% flat rate (37% above $1M) and aggregate method for withholding on bonuses.
- Publication 15-T: Federal Income Tax Withholding Methods (IRS.gov): The percentage-method withholding tables this calculator's federal tax logic is modeled on.
- 2026 Social Security Cost-of-Living Adjustment Fact Sheet (SSA.gov): The Social Security taxable maximum (wage base) this calculator applies.
- Questions and Answers for the Additional Medicare Tax (IRS.gov): The 0.9% Additional Medicare Tax rate and its withholding threshold.
Frequently asked questions
Why is my bonus taxed so much higher than my regular paycheck?
It usually isn't, at your actual tax rate; it just feels that way because of how bonuses are withheld. The IRS treats bonuses as "supplemental wages" and lets employers withhold at a flat 22% federal rate regardless of your real tax bracket, rather than running it through your W-4. If your true marginal rate is below 22%, the extra gets refunded (or reduces what you owe) when you file your return.
What's the difference between the percentage method and the aggregate method?
The percentage method withholds a flat 22% (37% on any amount that pushes your cumulative bonuses for the year past $1 million) and is what most employers use when a bonus is paid as a separate check. The aggregate method adds the bonus to one regular paycheck and withholds on the total at your annualized marginal rate, which employers sometimes use instead. Both are IRS-approved; your employer picks which one applies to you.
Does the flat 22% match what I'll actually owe in taxes on the bonus?
Not necessarily. 22% is a withholding rate, not your tax rate. If your marginal federal bracket is lower than 22%, you'll get the difference back as part of your refund (or a smaller balance due). If your bracket is higher, you'll owe more at filing time. The bonus doesn't have its own separate, permanent tax rate; it's taxed as ordinary income once your return is filed.
Does Social Security tax apply to bonuses?
Yes, at the same 6.2% rate as regular wages, up to the annual Social Security wage base ($184,500 for 2026). If your year-to-date wages have already reached that cap before the bonus is paid, no additional Social Security tax is withheld on it.
Is my bonus and salary information uploaded anywhere?
No. This calculator runs entirely in your browser. Nothing you enter is sent to a server or stored.