Tool · Investor Sam Windfall

Bonus Tax Gap: Will You Owe or Get a Refund?

July 1, 2026 • By the Investor Sam Editorial Team • Reviewed by Berly Sam Varghese, Editor
Employers withhold bonuses at a flat 22% supplemental rate — but your real marginal rate might be 32% or higher. If you spend the whole after-withholding amount, you could face a surprise tax bill in April. This calculator shows your true liability versus what was actually withheld, so you know exactly how much to set aside — or how big your refund will be.

Example: Bonus amount (gross): 25000 $ · Regular W-2 income this year (pre-bonus): 120000 $ · Federal tax already withheld from regular paychecks: 22000 $ · Bonus withholding rate your employer used: 22 % · Filing status (1=Single, 2=Married filing jointly): 1

Expected refund (positive) or amount owed (negative)$3,162
True federal tax on total income$24,339
Total federal tax withheld$27,500
Withheld from bonus specifically$5,500

Worked example

A $25,000 bonus on top of $120,000 salary (single filer) = $145,000 total income. After the $14,600 standard deduction, taxable income is $130,400. True federal tax: roughly $25,800. Salary withholding of $22,000 plus bonus withholding of $5,500 (22%) = $27,500 total withheld. Refund: about $1,700. But swap in a $200,000 salary and the bonus pushes you to the 32% bracket — and underpayment switches to a $2,400 tax bill.

Frequently asked questions

What is the supplemental withholding rate and why does it differ from my actual rate?

The IRS supplemental wage rate is 22% on amounts up to $1 million (37% above that). It is a simplified flat-rate deposit designed for easy payroll processing — it does not reflect your actual marginal rate, which is based on all your income for the year. The difference settles at filing.

Can I ask my employer to withhold more from my bonus?

Yes — you can submit an updated W-4 requesting additional withholding, or ask your employer if they can withhold at your actual marginal rate. Some payroll systems allow this; others apply the flat 22% automatically. Withholding extra from regular paychecks in advance is an alternative.

What happens if I significantly underpay during the year?

If you owe more than $1,000 in additional taxes and have not withheld or paid at least 90% of your current-year tax (or 100% of last year's), the IRS may impose an underpayment penalty. Paying estimated quarterly taxes after receiving a large bonus prevents this.

Does this calculator include state income tax withholding?

No — the calculation covers federal income tax only. State bonus withholding rules vary; some states use a flat rate, others use the same supplemental method as the IRS. Add your state rate to the gap calculation for a complete picture.

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Sources

Berly Sam Varghese · Editor, Investor Sam

Berly Sam Varghese is an engineer who treats money the way he treats any hard problem — something to be engineered, not gambled on. He funded years of education and built real financial stability the patient way, by living below his means and investing rather than borrowing. He writes for the person trying not to waste a rare opportunity. He reviews and approves every article on Investor Sam and checks the figures against primary sources before anything is published. More about our standards.