A bonus feels smaller than it should, and there is a reason: the IRS treats bonuses as supplemental wages, and supplemental wages are withheld at a flat 22% federal rate — no matter what tax bracket you are in. Missouri adds its own flat 4.7% supplemental rate. The example below is a $5,000 bonus for a single filer earning $60,000 a year in Missouri, paid separately from regular wages.
The breakdown: a $5,000 bonus in Missouri
| Line | Rate | Amount |
|---|---|---|
| Bonus (gross) | — | $5,000.00 |
| Federal income tax withheld | 22% | $1,100.00 |
| Missouri state tax withheld | 4.7% | $235.00 |
| Social Security | 6.2% | $310.00 |
| Medicare | 1.45% | $72.50 |
| Total withheld | 34.35% | $1,717.50 |
| You keep | 65.65% | $3,282.50 |
Other bonus sizes, same rates (assuming you are under the $184,500 Social Security wage base): a $1,000 bonus keeps $656.50 ($343.50 withheld); a $10,000 bonus keeps $6,565.00 ($3,435.00 withheld).
Withholding is not your tax — $500 comes back
The 22% federal withholding is deliberately high. Your actual federal tax on the bonus is your marginal rate: on a $60,000 salary your taxable income is $43,900, which sits in the 12% bracket — and a $5,000 bonus keeps you in it. So the real federal tax on the bonus is $600, not $1,100. The extra $500 is refunded when you file your return.
The same is true of the state tax for most people. Missouri's 4.7% withholding matches the top marginal rate, and on a $60,000 salary your marginal Missouri rate really is 4.7% — so the $235 is the tax you owe. On a lower salary your marginal rate is lower, and the difference comes back at filing too. Social Security and Medicare are exact: 6.2% and 1.45% of the bonus, with no refund.
All in, the true tax on a $5,000 bonus for this filer is $1,217.50 ($600 federal + $235 Missouri + $310 Social Security + $72.50 Medicare) — so after the refund you really keep $3,782.50, not $3,282.50. The $3,282.50 is just what lands on the bonus check.
What changes the number?
- How the bonus is paid. Paid separately, the flat 22% federal and 4.7% Missouri rates apply. Paid together with a regular paycheck, your employer usually uses the aggregate method instead — the withholding on that check is different, but the annual tax is identical.
- Your tax bracket. A higher earner in the 22% or 24% bracket owes more federal tax on the bonus, so less comes back. A lower earner in the 10% bracket gets more back.
- Very large bonuses. Once your supplemental wages from one employer pass $1,000,000 in a year, the excess is withheld at a mandatory 37% federal rate.
- Where you work. Kansas City and St. Louis each charge a 1% earnings tax, which is not included above. The Social Security wage base ($184,500 for 2026) also matters: if your salary plus bonus passes it, no Social Security is withheld on the part above it.
- The 22% rate has not changed. It has been 22% since 2018, the same as in 2025 — so a bonus taxed in 2025 was withheld exactly the same way.
Frequently asked questions
$1,717.50 is withheld: $1,100 federal income tax (22%), $235 Missouri tax (4.7%), $310 Social Security (6.2%) and $72.50 Medicare (1.45%). You keep $3,282.50 on the bonus check. Part of the federal withholding comes back when you file — see below.
Because withholding is not your tax. The IRS requires bonuses paid separately to be withheld at a flat 22% federal rate, whatever your bracket. Your actual tax on the bonus is your marginal rate — 12% on a $60,000 salary — so $500 of the $1,100 comes back as a refund when you file.
It is the flat supplemental withholding rate Missouri publishes for bonuses. On a $60,000 salary your marginal Missouri rate is also 4.7% (everything above $9,436 of taxable income), so the $235 withheld is also the tax you owe. On a lower salary your marginal rate is lower, and the difference comes back at filing.
Then your employer usually uses the aggregate method instead: the bonus is added to that pay period's wages and withholding is worked out on the combined amount. The withholding on that check looks different, but your annual tax is exactly the same — it all settles when you file.