Withholding is not taxation
A bonus feels punished because of one rule: employers may treat supplemental wages separately and withhold federal income tax at a flat 22%, whatever bracket you are actually in. The IRS says so in Publication 15, section 7. Nothing about your final tax bill changes — the bonus is ordinary income like any other. If that flat rate took more than your bracket needed, the difference comes back when you file; if it took less, you owe the gap.
Two details decide the rest. Above $1,000,000 of supplemental wages in a calendar year, the excess is withheld at 37% and the employer has no choice. And FICA never uses a flat trick: Social Security still stops at the annual wage base, Medicare never stops, which is why a bonus late in the year is often withheld less than an identical bonus in January.
The other method your employer may use
Instead of the flat rate, an employer may add the bonus to a regular paycheck and withhold as if the total were one payment — the aggregate method. On a modest bonus it usually withholds less than the flat rate; on a large one, considerably more, because a single fat paycheck looks like a very high annual salary to the payroll formula. You do not choose; your employer does. The calculator above shows the flat method, which is what most employers use for a separate bonus payment.
States that publish their own flat rate
Some states publish a supplemental rate of their own, and it is rarely the same as their regular rate. We only apply the ones we have read in the agency's document: Massachusetts (5% or 9% depending on the surtax threshold), Missouri (4.7%), North Carolina (4.09%), Oregon (8%), Wisconsin (banded, 3.54% to 7.65%). Every other state on this site has no verified flat supplemental rate — the honest answer there is the aggregate method, and the calculator says so instead of inventing a number.
Questions people ask
Is a bonus taxed at a higher rate than my salary?
No. It is withheld at a flat rate, usually 22% federally. Your tax bill treats the bonus exactly like salary; the withholding difference settles at filing time.
Why was almost nothing taken out for Social Security?
Because Social Security stops at the annual wage base ($184,500 in 2026). If your regular pay already reached it, the bonus carries no Social Security line at all — only Medicare.
Will I get some of it back?
Often, yes. If the flat 22% exceeded what your bracket actually owed on that income, the excess comes back as a refund. That is a withholding overshoot, not a bonus tax.
Does my state take its own cut?
It depends on the state and this page says which ones publish a flat supplemental rate. Where none exists, your employer applies the state's normal withholding method to the combined payment.