Bonus Tax Calculator — 22% Flat vs Aggregate Method
Compare the IRS percentage (flat 22%) and aggregate methods for federal tax withheld on a bonus, plus FICA. Free, in-browser TY2025 estimate.
About Bonus Tax Calculator
A bonus tax calculator compares the two IRS methods an employer can use to withhold federal income tax from a bonus, which the IRS treats as supplemental wages. The percentage (flat) method withholds a flat 22% of the bonus — rising to 37% on any amount above $1 million in a year. The aggregate method instead adds the bonus to a regular paycheck and withholds at the rate implied by your marginal bracket. Either way, FICA still applies: Social Security at 6.2% up to the $176,100 wage base, Medicare at 1.45%, plus the 0.9% additional Medicare tax on wages over $200,000. Withholding is not your final tax — it settles when you file your return. This is a TY2025 estimate, not tax advice.
Use cases
- See why your bonus looked so heavily taxed. A bonus often arrives with a big chunk withheld, which can feel like a punishing tax rate. The flat 22% method is the usual reason: it withholds a fixed 22% regardless of your bracket, plus FICA. Running your bonus through both methods shows what was likely taken and why the deposit was smaller than the headline number, without treating the withholding as your real tax.
- Compare flat vs aggregate before payday. If your employer tells you which method they use, or you simply want to plan, comparing the two side by side shows how much each would withhold. For higher earners the aggregate method can withhold more than the flat 22%; for lower brackets the flat method can over-withhold, which tends to come back as a refund at filing time.
- Estimate the cash you'll actually keep. Beyond withholding, you want the take-home figure. The calculator subtracts estimated federal withholding and FICA from the gross bonus, so you can budget around the real amount that lands in your account rather than the gross number on the offer letter or pay notice.
- Plan for the true tax at filing. Because withholding rarely equals your final tax, a bonus can leave you owing a little more or getting some back. The aggregate, marginal figure is usually closer to your real tax, so comparing it with the flat method hints at whether to expect a bill or a refund and whether to adjust your regular withholding.
- Check the million-dollar and wage-base edges. For very large bonuses, the portion above $1 million is withheld at 37% under the flat method, and Social Security stops once your year's wages pass the $176,100 base. Testing these edges shows how the treatment changes for big bonuses or late-year payouts made after the wage base has already been met.
How it works
- Enter your bonus amount. Type the gross bonus (supplemental wages) before any withholding is taken out.
- Choose the withholding method. Select percentage (flat 22%) or aggregate, or view both side by side to compare the two results.
- For the aggregate method, add pay details. Enter your regular paycheck and filing status so the tool can estimate the marginal rate applied to the combined amount.
- Include year-to-date wages if relevant. Adding wages already earned lets the tool apply the $176,100 Social Security cap and the $200,000 additional-Medicare threshold correctly.
- Read the withholding and net. The tool shows federal withholding under each method, FICA, and the estimated take-home bonus, noting that this is withholding, not final tax.
Examples
Input: $10,000 bonus, flat 22% method
Output: $2,200 federal withheld plus $765 FICA
Flat method: 22% of 10,000 is 2,200; FICA of 7.65% (6.2% + 1.45%) is 765, assuming you are under the wage base.
Input: $5,000 bonus, aggregate method, 24% bracket
Output: About $1,200 federal withheld plus $382.50 FICA
The aggregate method ties withholding to your marginal rate, so a 24% bracket withholds more than the flat 22% would.
Input: $1,200,000 bonus, flat method
Output: $294,000 federal withheld (before FICA)
22% on the first $1,000,000 (220,000) plus 37% on the $200,000 above it (74,000) equals 294,000.
Frequently asked questions
Why is 22% withheld from my bonus?
Under the IRS percentage method, employers withhold a flat 22% from supplemental wages like bonuses, no matter your tax bracket. It is a withholding rule, not your actual tax rate — the difference is reconciled when you file.
What is the difference between the flat and aggregate methods?
The flat (percentage) method withholds a fixed 22% on the bonus alone. The aggregate method lumps the bonus in with a regular paycheck and withholds based on your marginal bracket, which can be higher or lower than 22% depending on your income.
Is 22% the most that will be withheld?
For bonuses under $1 million in a year, the flat rate is 22%. Any portion above $1 million is withheld at 37% under the mandatory higher rate. The aggregate method has no single cap — it follows your bracket.
Does FICA come out of a bonus too?
Yes. Social Security (6.2% up to the $176,100 wage base) and Medicare (1.45%, plus 0.9% additional on wages over $200,000) apply to bonuses under both methods, on top of income-tax withholding.
Will I get some of the withholding back?
Possibly. If the flat 22% withheld more than your bracket requires, the excess comes back as a refund; if it withheld too little, you may owe. The aggregate, marginal figure is usually closer to your true tax.
Does this include state taxes on my bonus?
No. Many states have their own supplemental-wage withholding rates, and this calculator does not model them. It estimates only federal withholding and FICA — check your state separately.
Is my bonus figure saved anywhere?
No. All calculations run in your browser; nothing you enter is uploaded or stored.
Pro tips
- Ask payroll which method they use — flat vs aggregate can change your take-home noticeably.
- Treat the withheld amount as a deposit toward your tax, not the tax itself; reconcile it at filing.
- If the flat 22% over-withholds for your bracket, expect part of it back rather than trying to change it mid-year.
- For a very large bonus, remember the portion over $1 million is withheld at 37%.
- Check whether your year-to-date wages have passed the $176,100 Social Security cap — bonuses after that point skip the 6.2% piece.
Reviewed by Ahsan Mahmood · Last updated 2026-07-08 · Part of ZTools.
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