Bonus Tax Calculator
Created by: James Porter
Last updated:
Compare the supplemental flat-rate method (22%) versus the aggregate method for bonus withholding, including FICA and state taxes, to see your net bonus under both approaches.
Bonus Tax Calculator
FinanceEstimate federal and state taxes on a bonus using both IRS-approved withholding methods. Compare net bonus under each approach.
What is a Bonus Tax Calculator?
A bonus tax calculator estimates the federal, FICA, and state taxes withheld from a bonus or supplemental income payment.
It compares the two main IRS-approved withholding methods — the supplemental flat rate and the aggregate method — so you can understand how much of your bonus will actually land in your bank account.
Bonuses often feel more heavily taxed than regular pay because employers withhold at a higher rate upfront.
That extra withholding is not a penalty — it is simply a large lump-sum payment being processed through a payroll system designed for smaller recurring paychecks.
A practical bonus tax tool should show both withholding methods, the resulting net bonus under each, and a reminder that your actual tax liability is finalized when you file your annual return, not at the time of withholding.
How Bonus Tax Withholding Works
Under the supplemental rate method, employers withhold a flat 22% federal tax on any bonus up to $1 million in a calendar year and 37% on any portion above that.
This is the default method used by most payroll systems because it is simple to administer.
Under the aggregate method, the employer adds the bonus to the employee's most recent regular paycheck, recalculates annualized withholding based on the combined amount, then subtracts what was already withheld from regular wages.
This can result in higher or lower withholding depending on where the combined income lands in the tax brackets.
In both cases, FICA taxes (Social Security up to the wage base plus Medicare) apply to the bonus amount in addition to the federal income tax withholding.
Core bonus withholding relationships
Supplemental federal withholding = bonus × 22% (for bonus portion under $1M)
FICA on bonus = bonus × 6.2% (SS, up to wage base remaining) + bonus × 1.45% (Medicare)
Net bonus = gross bonus - federal withholding - FICA - state withholding
Example Scenarios
Example 1: $10,000 bonus, 22% bracket
At 22% supplemental withholding plus 7.65% FICA plus a 5% state rate, a $10,000 bonus might net roughly $6,535 after withholding — about 65 cents on the dollar before any filing adjustment.
Example 2: High earner, aggregate method
For someone already in the 35% bracket, the aggregate method will produce higher withholding than the flat 22%, reducing net pay more than the supplemental rate would.
Example 3: Lower-bracket worker
If your marginal rate is 12% but the supplemental method withholds 22%, you will likely receive a partial refund when filing because more federal tax was withheld than you actually owe on the bonus.
How People Use This Calculator
- Estimate how much of a performance bonus or year-end bonus you will take home after withholding.
- Compare supplemental and aggregate withholding to understand which method your employer uses.
- Plan for a large bonus by knowing approximately how much to set aside for tax filing adjustments.
- Evaluate signing bonuses or spot bonuses when comparing job offers.
Tips for Better Bonus Tax Planning
Withholding and tax liability are not the same thing.
If too much is withheld, you get a refund.
If too little is withheld, you may owe at filing.
Check your total withholding for the year before assuming the bonus withholding alone tells the full story.
Timing a bonus near year-end can matter.
If you expect your income to be significantly different next year, receiving a bonus in January versus December can shift you into a different bracket for that year.
Frequently Asked Questions
Why are bonuses taxed so heavily?
Bonuses are supplemental income and the IRS requires employers to withhold at least 22% for federal taxes using the flat rate method. That rate can feel steep compared to a paycheck but is not a different tax — it just front-loads the withholding. Your actual liability is settled when you file.
What is the supplemental rate method?
The supplemental rate method withholds a flat 22% federal tax on bonuses up to $1 million and 37% on any amount above that, regardless of your normal tax bracket.
What is the aggregate withholding method?
The aggregate method adds your bonus to your most recent regular paycheck to estimate your annualized income, then calculates withholding based on that combined amount. It can result in more or less withholding than the flat rate depending on your income level.
Will I get money back if too much is withheld from my bonus?
Yes. Over-withholding on a bonus increases your expected refund when you file your annual return. The bonus itself is taxed at your ordinary income rate, not a special bonus rate.
Sources and References
- IRS Publication 15 (Employer's Tax Guide) on supplemental wages and withholding methods.
- IRS Revenue Procedure covering the optional flat-rate and aggregate withholding methods for supplemental pay.