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Bonus Tax Calculator

Calculate taxes on bonuses using supplemental flat rate or aggregate method with net-to-gross calculation for target net bonuses.

Tested tool guide Tested browser tools Checked August 16, 2026

What Bonus Tax Calculator does and how it behaves

Bonus withholding can differ substantially depending on whether payroll treats the payment separately or combines it with regular wages. This calculator estimates the gross bonus, withheld amounts, and resulting net under the supplemental flat-rate and aggregate methods. It can also work backward from a desired take-home bonus to the required gross payment. The important distinction is that calculated withholding is a payroll prepayment, not the employee's final income tax on the bonus.

How the result is produced

1

Supplemental flat-rate method

In flat-rate mode, the bonus is treated as separately identified supplemental wages. The applicable supplemental withholding rate is applied directly to the gross bonus. The calculator then uses the included withholding amounts to determine the estimated take-home payment. This result describes what may be withheld from the bonus check, not the employee's eventual marginal tax rate.

2

Aggregate and gross-up calculations

Aggregate mode combines the bonus with regular wages for a single payroll-period withholding calculation, then attributes the increase over regular-wage withholding to the bonus. Net-to-gross reverses the calculation: it determines the gross bonus needed to leave the requested net amount after included withholding. Under the aggregate method, that gross-up need not equal the target divided by one minus a single rate.

Good uses

  • Compare the estimated take-home amount when payroll can use either separate supplemental withholding or the aggregate method.
  • Estimate how much of an upcoming bonus check will remain after the withholding components represented in the calculator.
  • Determine the gross bonus an employer must authorize when an employee has been promised a specific net bonus.

Limits and checks

  • Do not interpret the withheld amount as the final tax attributable to the bonus. Final federal income tax is determined from the employee's full-year return.
  • An aggregate result depends on regular wages, payroll frequency, and the employee's withholding information. Inputs from a different pay period can materially change the estimate.
  • Check which payroll items the result includes. State or local withholding, benefit deductions, garnishments, and year-to-date payroll-tax effects can make the actual check differ.

Common questions

Why can the aggregate method withhold more than the flat-rate method?

The aggregate method calculates withholding after adding the bonus to regular wages for that payroll period. The combined amount can produce a larger incremental withholding result under the employee's payroll settings. That does not necessarily mean the bonus is ultimately taxed at a special higher rate, because final income tax is reconciled on the annual return.

Can this calculator tell me exactly how much tax I will owe on my bonus?

No. It estimates withholding from the payment. The eventual tax outcome depends on annual income, filing status, deductions, credits, other withholding, and other return information. A bonus is compensation included in income, while the amount withheld from its paycheck is only a payment toward the employee's total tax liability.

References and verification

The behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.

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