Bonus Tax Calculator: How Supplemental Wages Are Withheld

If you searched for a bonus tax calculator, you probably want to know how much of your bonus you will actually take home. Bonuses are “supplemental wages” under IRS rules, and employers can withhold taxes on them differently than regular paychecks. This guide explains the two withholding methods, walks through a worked example, and helps you plan around the result.

Key Takeaways

• Employers withhold bonuses at a flat 22% federal rate or using the aggregate method — both are just withholding, not your final tax rate.
• Your actual tax on the bonus depends on your marginal tax bracket for the year.
• Bonuses are also subject to Social Security (6.2%) and Medicare (1.45%) payroll taxes.
• If your bonus pushes you into a higher bracket, only the income above the threshold is taxed at the new rate.

Quick Calculator

How Bonuses Are Withheld: Two Methods

Employers choose one of two IRS-approved methods for withholding federal income tax on supplemental wages like bonuses:

1. Flat Rate Method (Most Common)

The employer withholds a flat 22% for federal income tax on the bonus amount. This is the default for most payroll systems when the bonus is paid separately from regular wages. If your supplemental wages exceed $1 million in a calendar year, the rate jumps to 37% on the excess.

Example: A $10,000 bonus withheld at the flat rate:

• Federal income tax: $10,000 × 22% = $2,200
• Social Security: $10,000 × 6.2% = $620 (if under the wage base)
• Medicare: $10,000 × 1.45% = $145
• Net bonus: ~$7,035 (before state taxes)

2. Aggregate Method

The employer adds the bonus to your regular paycheck for that pay period, calculates withholding on the combined total as if it were a single paycheck, then subtracts the withholding already applied to the regular portion. This often results in higher withholding because the combined amount may land in a higher bracket for that pay period.

For a deep dive into both methods and when each applies, see how bonuses are taxed.

Withholding Is Not Your Final Tax

The 22% flat rate is a withholding rate, not a tax rate. Your actual tax depends on your marginal tax bracket for the full year. If your effective tax rate is lower than 22%, you will get the difference back as a refund. If it is higher, you may owe more at filing time.

This is why a bonus tax calculator is a starting point. For a full-year estimate, use our federal income tax calculator or the taxable income calculator to see where the bonus lands in your bracket structure.

How to Reduce Bonus Tax Impact

1. Maximize pre-tax contributions. Increasing your 401(k) deferral or HSA contribution before the bonus hits reduces the taxable portion. Some employers let you set a separate deferral rate for bonus paychecks.
2. Adjust your W-4. If the flat 22% rate consistently over-withholds, update your W-4 to claim additional deductions or reduce extra withholding.
3. Time deductions. If you are close to a bracket boundary, charitable bunching or other itemized deductions can offset a bonus that pushes you higher.
4. Check estimated payments. If you receive large bonuses and owe at filing, consider estimated tax payments to avoid the underpayment penalty.

Common Mistakes

• Thinking 22% is the tax rate. It is only the withholding rate. Your actual rate depends on your full-year income and filing status.
• Forgetting payroll taxes. Bonuses are subject to FICA taxes — Social Security (6.2% up to $176,100 in 2025 / $183,000 in 2026) and Medicare (1.45% with no cap). High earners may also owe the 0.9% Additional Medicare Tax.
• Ignoring state taxes. Most states tax bonuses as ordinary income. Factor state withholding into your net estimate.
• Overlooking the aggregate method. If your bonus is combined with a regular paycheck, the higher withholding is temporary — you get it back at filing if you were over-withheld.

When to Re-Run the Calculator

Re-run the bonus tax calculator whenever you receive a new bonus, change jobs, adjust your W-4 withholding, or shift retirement contributions. Even a small change can swing a tax refund into a balance due.

How sharper.tax Helps

The quick calculator above gives you a fast estimate from a few inputs. sharper.tax goes further — we analyze your actual tax return, compute your real effective tax rate, and show exactly how bonus income interacts with your bracket structure. We surface strategies like tax-loss harvesting or retirement contribution timing that can offset the impact. The tax code is complicated, but better tools have leveled the field.

Sources

• IRS Publication 15-T (Federal Income Tax Withholding Methods)
• IRS Publication 15 (Circular E, Employer’s Tax Guide)
• IRS Topic 751: Social Security and Medicare Withholding Rates

The information above is educational and not tax advice.