What Is a Bonus Tax Calculator and How Is It Calculated?
A bonus tax calculator estimates how much of a work bonus is withheld for federal, Social Security, Medicare, and state taxes before it reaches your bank account. The IRS treats bonuses as supplemental wages, taxed differently from your regular salary using one of two withholding methods your employer chooses.
Under the flat (percentage) method, employers withhold a straight 22% federal rate on bonuses up to $1 million in a calendar year — 37% on any amount above that — per IRS Publication 15. Under the aggregate method, the bonus is added to your most recent regular paycheck and taxed as one lump sum at your marginal income tax rate, which is often higher than 22% for mid-to-high earners.
According to the IRS, both methods are only about withholding timing — the total federal income tax you actually owe on the bonus for the year is the same either way once you file your return; only the amount withheld upfront differs.
How to Use This Bonus Tax Calculator
Enter your bonus and pay details and both withholding methods update instantly, side by side. Here is what each field means:
- Bonus Amount: The gross bonus before any taxes are withheld.
- Regular Annual Salary: Your regular gross salary, excluding this bonus. This determines the tax bracket the bonus falls into under the aggregate method.
- Filing Status: Single, Married Filing Jointly, or Head of Household — sets your federal tax brackets and standard deduction.
- State Tax Rate on Bonus: Your state's flat supplemental withholding rate, if any. Enter 0 for Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington, or Wyoming — the nine states with no wage income tax.
This calculator works for any US state: enter your state's bonus withholding rate directly, since supplemental rates vary widely — for example California withholds 10.23% on bonuses while nine states withhold 0%.
Flat vs. Aggregate Bonus Withholding: What the Difference Means
Which method leaves more in your paycheck depends on your regular salary. If your marginal federal tax bracket is below 22% (roughly under $48,475 in taxable income for a single filer in 2025), the aggregate method usually withholds less. If your bracket is above 22% — common once salary plus bonus pushes taxable income past that point — the flat method usually withholds less, since it caps federal withholding at a flat 22% regardless of your true marginal rate.
| Method | Federal Withholding Rate | Best For |
|---|---|---|
| Flat (percentage) method | Flat 22% (37% above $1M) | Higher earners in a 24%+ marginal bracket — withholds less than their true rate |
| Aggregate method | Your marginal rate on salary + bonus combined | Lower earners in a 10–12% bracket — withholds closer to what they actually owe |
Social Security (6.2% up to the $176,100 2025 wage base) and Medicare (1.45%, plus 0.9% additional Medicare above $200,000 for single filers or $250,000 for joint filers) are withheld identically under both methods, since FICA does not depend on which federal income-tax method your employer uses.
Frequently Asked Questions
Why are bonuses taxed at a higher rate than regular pay?
Bonuses are not taxed at a higher rate overall — they are withheld differently. The IRS classifies bonuses as supplemental wages and lets employers withhold a flat 22% federal rate instead of running them through the regular payroll tax tables, which can feel like more tax but is only a difference in upfront withholding, not your final tax bill.
How accurate is this bonus tax calculator?
This calculator uses the 2025 IRS supplemental wage flat rate, the 2025 federal income tax brackets and standard deduction, and current FICA rates and thresholds. It does not model state-specific standard deductions, local payroll taxes, retirement plan deferrals, or year-to-date wages toward the Social Security cap from prior paychecks — for a paycheck-exact figure, use your payroll provider's calculation or consult a tax professional.
What is the difference between the flat method and the aggregate method?
The flat method applies a straight 22% federal withholding rate to the bonus alone, separate from your regular paycheck. The aggregate method combines the bonus with your most recent regular paycheck and withholds tax on the total as if it were one larger paycheck, taxed at your marginal rate. Employers can choose either method; only method changes withholding timing, not your total annual tax liability.
How do I get more of my bonus after taxes?
You cannot change which withholding method your employer uses, but you can reduce your taxable income by increasing pre-tax 401(k) or HSA contributions in the same pay period as the bonus, which lowers the wages subject to both federal and FICA withholding. If withholding leaves you overpaid for the year, the excess comes back as a refund when you file — use the Tax Withholding Calculator to check your full-year position.