Bonus Tax Calculator
Estimate a 2026 U.S. bonus paycheck after deferrals, supplemental federal withholding, FICA, state/local rate, and warning checks.- {{ warning }}
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Introduction
Bonus pay is usually treated as supplemental wages in U.S. payroll. That matters because a bonus check can be withheld differently from regular pay, even though the withholding is still only a prepayment toward the employee's eventual federal income tax return.
A bonus estimate is most useful before the payroll run happens. A sales commission, annual performance bonus, severance payment, or one-time award can be reduced by retirement deferrals, federal supplemental wage withholding, Social Security tax, Medicare tax, Additional Medicare tax, and state or local withholding. The final bank deposit can be much lower than the announced gross bonus.
Withholding and final tax are not the same number. A flat supplemental wage withholding rate can be lower or higher than the employee's real marginal federal tax rate, and aggregate withholding can change when regular pay, pay frequency, filing status, W-4 credits, or the Step 2 checkbox schedule changes.
A careful estimate keeps the payroll question narrow: what might this bonus paycheck withhold under a stated method and stated assumptions? It does not replace payroll records, Form W-4 review, state-specific rules, or year-end tax filing calculations.
How to Use This Tool:
Start with the bonus check you expect, then add only the payroll assumptions that apply to that same payment.
- Enter Gross bonus before taxes, retirement elections, or other pre-tax reductions. The summary updates to show the estimated net bonus, taxable bonus, take-home rate, and selected federal method.
- Choose Federal withholding method. Use Percentage method for a separately identified bonus check that uses the supplemental rate. Use Aggregate method when the bonus is combined with regular wages or when payroll applies the Pub. 15-T regular wage calculation.
- Add Income-tax pre-tax bonus deferral and Prior supplemental wages this year. Prior supplemental wages matter when the current payment crosses the $1 million supplemental wage threshold.
- For aggregate comparisons, enter Regular taxable wages this pay period, Pay frequency, and W-4 filing status. Open Advanced for W-4 Step 3 credits, Step 4(a) other income, Step 4(b) deductions, Step 4(c) extra withholding, the Step 2 checkbox schedule, or an actual regular federal withholding override.
- Enter YTD FICA wages before bonus so Social Security tax can stop at the 2026 wage base. If part of a deferral also reduces Social Security and Medicare wages, enter that amount in FICA-exempt part of deferral.
- Add a verified State and local supplemental rate if it applies. Leave it at 0 only for a federal-only estimate, then review the warning list if the tool flags missing state/local withholding, capped deferrals, wage-base limits, or negative net cash.
- Read Bonus Paycheck first, then use Federal Method Comparison, Tax Line Ledger, Assumption Review, and Bonus Take-home Split to check the calculation before copying a row or exporting a table.
If an error appears, fix the named field before using the result. Negative dollar fields are not accepted, rates must stay from 0% to 100%, and overly large deferral entries are capped with warnings rather than allowed to push taxable wages below zero.
Interpreting Results:
Estimated net bonus is the cash-planning number, not a promise from payroll. Use it with the selected method badge and the warning list; a large take-home amount can simply mean state/local withholding is set to 0%, regular wages are missing for aggregate mode, or FICA wages already exceed the Social Security wage base.
Federal Method Comparison shows why two payroll runs with the same gross bonus can withhold different federal income tax. The percentage method applies the supplemental wage rates to the income-taxable bonus. The aggregate method annualizes regular wages plus the below-threshold taxable bonus, subtracts regular federal withholding, and assigns the remaining federal withholding to the bonus.
Tax Line Ledger is the audit trail. Check the taxable base for federal income withholding, Social Security, Medicare, Additional Medicare, and state/local withholding before trusting the net result. A federal withholding gap below the marginal-tax estimate does not prove a balance due, and a gap above it does not guarantee a refund; it only compares modeled withholding with the planning rate entered in Advanced.
When the estimate differs from a pay stub, first check pay frequency, regular taxable wages, the federal method, YTD FICA wages, W-4 entries, deferral treatment, and the state/local rate. Differences after those checks usually come from employer payroll setup, local rules, benefit coding, or rounding outside this estimate.
Technical Details:
Supplemental wage withholding separates the payroll timing problem from the final tax-return problem. Federal income tax withholding on a bonus can use a flat supplemental wage rate, an aggregate calculation based on regular wages, or a mandatory high supplemental wage rate once cumulative supplemental wages for the employee exceed $1 million during the calendar year.
The estimate starts by separating cash received from tax bases. An income-tax pre-tax deferral reduces the income-taxable bonus and the cash available from the check. Social Security and Medicare use a separate FICA taxable bonus, because a common retirement deferral may reduce federal income-taxable wages without reducing FICA wages.
Formula Core
Two intermediate bases drive most of the result:
| Quantity | Formula or rule | Why it matters |
|---|---|---|
| Income-taxable bonus | max(0, gross bonus - income-tax pre-tax bonus deferral) |
Used for federal income withholding and, by default, state/local withholding. |
| FICA taxable bonus | max(0, gross bonus - FICA-exempt part of deferral) |
Used for Social Security, Medicare, and Additional Medicare estimates. |
| Take-home rate | net bonus / gross bonus |
Shows how much of the gross bonus remains as estimated cash. |
Federal supplemental wage withholding is split before the selected federal method is applied. The part of the income-taxable bonus that keeps cumulative supplemental wages at or below $1 million can use the 22% percentage method or the aggregate method. Any excess over the $1 million threshold is modeled at 37% regardless of Form W-4.
| Federal component | Calculation basis | Rate or schedule | Boundary |
|---|---|---|---|
| Percentage method | Income-taxable supplemental wages below the mandatory threshold | 22% | Applies while cumulative supplemental wages do not exceed $1,000,000. |
| Mandatory high supplemental portion | Income-taxable supplemental wages above the threshold | 37% | Applies to the excess after cumulative supplemental wages exceed $1,000,000. |
| Aggregate method | Regular taxable wages plus below-threshold income-taxable bonus wages | 2026 Pub. 15-T percentage method schedule | Subtracts regular federal withholding, then adds any mandatory high supplemental portion. |
For aggregate method calculations, period wages are annualized before the 2026 Pub. 15-T schedule is applied. The adjusted annual wage amount is:
The tentative annual withholding comes from the selected filing-status schedule and the standard or Form W-4 Step 2 checkbox schedule. W-4 Step 3 credits reduce tentative annual withholding but not below zero. The remaining annual amount is divided by pay periods per year, Step 4(c) extra withholding is added, and regular federal withholding is subtracted so only the bonus portion remains.
| Tax line | Taxable base | Rate | Limit or note |
|---|---|---|---|
| Social Security tax | FICA taxable bonus up to remaining 2026 wage-base room | 6.2% | 2026 wage base is $184,500, reduced by YTD FICA wages before the bonus. |
| Medicare tax | All FICA taxable bonus wages | 1.45% | No wage base limit. |
| Additional Medicare tax | FICA taxable bonus wages paid after employer-paid wages exceed $200,000 | 0.9% | Employer withholding threshold is applied without regard to filing status. |
| State/local withholding | Income-taxable bonus by default, or gross bonus when the Advanced switch is off | User entered | No state or local supplemental wage lookup is performed. |
Warnings are part of the calculation surface, not decoration. They identify assumptions that commonly change a bonus paycheck:
| Warning condition | What to check |
|---|---|
| Aggregate method selected with zero regular taxable wages | Enter the regular paycheck amount for the same payroll period or switch to percentage method. |
| Bonus crosses the $1 million supplemental wage threshold | Review the 37% federal withholding portion in the Tax Line Ledger. |
| Income-tax or FICA-exempt deferral is capped | Check whether an annual election was entered into a per-bonus field. |
| Social Security wage base limits part of the bonus | Confirm YTD FICA wages before comparing with a pay stub. |
| Negative net cash | Review deferrals, state/local rate, method choice, and whether a rate or dollar amount was entered in the wrong field. |
Accuracy and Privacy Notes:
This is an educational payroll estimate for U.S. federal 2026 withholding assumptions. It is not tax, legal, financial, or payroll advice, and it does not decide final tax due on a return.
- State and local supplemental wage rules are not looked up. The state/local rate is whatever rate the user enters.
- Employer payroll systems can differ because of benefit coding, rounding, payroll-period history, local taxes, and settings not represented by the exposed W-4 fields.
- Additional Medicare withholding uses the employer $200,000 withholding threshold, which can differ from final filing-status liability thresholds.
- The estimate does not connect to a payroll account, tax account, or state tax database.
Worked Examples:
A $15,000 bonus with a $1,500 income-tax pre-tax deferral, $92,000 in YTD FICA wages, a 5% state/local rate, and Percentage method selected leaves a $13,500 income-taxable bonus. Bonus Paycheck shows $2,970 of federal income tax withholding, $930 of Social Security tax, $217.50 of Medicare tax, $675 of state/local withholding, and about $8,707.50 as Estimated net bonus. Federal Method Comparison also shows that aggregate federal withholding would be about $4,183.70 with the default biweekly regular wages and single filing status.
A threshold case starts with $950,000 of prior supplemental wages and a new $120,000 bonus. Only $50,000 remains under the $1 million supplemental wage threshold, so Tax Line Ledger models $11,000 at the 22% supplemental rate and $25,900 at the 37% mandatory high supplemental rate. With $170,000 in YTD FICA wages, only $14,500 of the bonus remains subject to Social Security tax, and Additional Medicare withholding applies to $90,000 after the employer-paid wage total passes $200,000.
A troubleshooting example is a $5,000 bonus with a $4,800 income-tax deferral, aggregate method, no regular taxable wages, and a 20% state/local rate. The estimate can show negative net cash because the deferral, FICA taxes, and state/local withholding exceed the remaining cash. The warning list points to the zero regular taxable wages in aggregate mode and the negative net result, which are the first fields to check.
FAQ:
Why is bonus withholding different from my regular paycheck?
Bonuses are usually supplemental wages. A separately identified bonus can use the 22% percentage method below the $1 million threshold, while a combined regular-plus-bonus payment can use the aggregate method based on regular wages, pay frequency, filing status, and W-4 settings.
Does a 22% federal withholding rate mean my bonus is taxed at 22%?
No. The 22% rate is a payroll withholding method for eligible supplemental wages, not the final income tax rate on the bonus. The Federal marginal-tax estimate field compares withholding with a planning rate, but the final result depends on the full tax return.
Which state rate should I enter?
Enter a combined state and local supplemental withholding rate you have verified from payroll or current state guidance. The calculator does not choose a state, detect local taxes, or look up state supplemental wage methods.
Why did Social Security tax shrink or disappear?
The calculation uses YTD FICA wages before bonus against the 2026 Social Security wage base of $184,500. Once the remaining wage-base room is used, the estimate stops Social Security tax on the rest of the bonus while Medicare tax continues.
What should I fix when an error appears?
Read the error text and correct the named field. Negative dollar inputs are invalid, State and local supplemental rate and Federal marginal rate estimate must stay from 0% to 100%, and a negative regular withholding override is rejected.
Glossary:
- Supplemental wages
- Wage payments outside regular wages, such as bonuses, commissions, severance, awards, or back pay.
- Percentage method
- The federal supplemental wage method that withholds 22% on eligible below-threshold supplemental wages.
- Aggregate method
- A method that combines regular wages and supplemental wages, calculates regular payroll withholding, then assigns the extra withholding to the bonus.
- Income-taxable bonus
- The gross bonus after income-tax pre-tax bonus deferral, used for federal income withholding and the default state/local base.
- FICA
- Federal payroll taxes for Social Security and Medicare on covered wages.
- Social Security wage base
- The annual wage ceiling for Social Security tax, set to $184,500 for 2026 in this estimate.
- Additional Medicare tax
- An extra 0.9% Medicare withholding amount modeled after employer-paid wages exceed $200,000 in the calendar year.
- W-4 Step 2 checkbox
- A Form W-4 setting that uses a different Pub. 15-T withholding schedule for the aggregate method.
References:
- Publication 15 (2026), Employer's Tax Guide, Internal Revenue Service, updated April 30, 2026.
- Publication 15-T (2026), Federal Income Tax Withholding Methods, Internal Revenue Service, updated April 30, 2026.
- Contribution and Benefit Base, Social Security Administration.
- Topic no. 751, Social Security and Medicare withholding rates, Internal Revenue Service, updated January 20, 2026.
- Topic no. 560, Additional Medicare tax, Internal Revenue Service, updated May 15, 2026.