The flat 22% on supplemental wages
For 2026 the federal withholding rate on supplemental wages is 22%. Bonuses, commissions, overtime and taxable fringe benefits paid separately from regular wages are withheld at that one rate, because an employer has no bracket table to apply to a one-off payment.
The page multiplies the payment by 22% and prints the result beside the payment itself, so the gap between gross and net is arithmetic rather than a mystery. A $10,000 bonus carries $2,200 of federal income tax withholding, and $7,800 reaches the account.
The rate was made permanent by P.L. 119-21, which extended the individual rates first enacted by P.L. 115-97. It is a withholding rate, not a statement about what the bonus will finally cost you, which is the distinction the rest of the page keeps returning to.
The 37% above $1,000,000
Once a single employee has received more than $1,000,000 of supplemental wages from an employer in a calendar year, the excess is withheld at 37% - the top income tax rate for the year - without regard to the Form W-4 on file.
The million is a per-employee, per-year line rather than a per-payment one, so a payment that straddles it is split between the two rates. That is what the second field is for: with $900,000 already paid this year, a $250,000 bonus has $100,000 withheld at 22% and $150,000 at 37%, for $77,500 in total.
Payments from businesses under common control are added together before the line is applied, which is why the calculator asks what has already been paid rather than judging each payment on its own.
Why your return settles the difference
Withholding at 22% is too little for a bonus that lands on top of a salary already in the 24%, 32% or 35% bracket, and too much for someone whose whole year sits lower. Either way the bonus joins ordinary income on the return and is taxed at your own rate, so the difference appears in the refund or the balance due.
Payroll taxes are a separate account. Social Security at 6.2% applies up to the $184,500 wage base for 2026, Medicare at 1.45% has no cap, and wages over $200,000 also carry the 0.9% Additional Medicare Tax. None of that is part of the withholding figure, which is why the drop from gross to net can look much steeper than 22%.
For the same reason, the "bonus after withholding" statistic subtracts only the federal income tax shown. It is not a take-home figure, because FICA comes off the same paycheck on its own lines.
What this page does not price
It prices the federal income tax withheld on this payment, not your final tax. State income tax sits outside the model, and many states withhold on supplemental wages at a flat rate of their own, so the same bonus can land very differently in two states.
A bonus paid to a contractor rather than an employee is not supplemental wages at all: it arrives on a 1099 and is taxed through self-employment tax and the ordinary brackets. Employer stock and options carry their own withholding rules as well.
An estimate, not a return, and not tax advice. Enter a payment of zero and it says plainly that nothing is withheld, rather than printing a plausible-looking figure to fill the space.
Why 22% is not the tax on the bonus
The flat rate is a withholding instruction, not a bracket. It exists because an employer cannot know what a one-off payment will do to a year of income, so the law gives them one rate to apply and leaves the reconciliation to the return. The bonus is taxed at your own marginal rate either way; only the money sent to the IRS in advance changes.
The counterexample runs in both directions. A single filer whose salary already sits in the 32% band has $2,200 withheld from a $10,000 bonus and owes about $3,200 on it, so the $1,000 difference is a smaller refund or a larger balance due in April. A filer in the 12% band has the same $2,200 withheld and owes $1,200, so $1,000 comes back. The withholding was identical; the outcomes are not.
That is also why "withheld at 22%" and "taxed at 22%" are different sentences, and why the page prints only the first. Reading the second into it is the mistake that makes a bonus feel as though it were taxed twice.
Danfio