A bonus is supplemental wages. It does not have to run through Form W-4 the same way as regular pay. Publication 15 section 7 gives two methods when the bonus is identified separately:
- Optional flat 22% (no other percentage allowed). Most payroll systems pick this.
- Aggregate method. Add the bonus to regular wages for the period, tax the total with the percentage method, subtract the tax on regular wages.
Above $1 million of supplemental wages in the calendar year, a mandatory 37% applies to the excess, without regard to the W-4.
Default: $1,000 bonus → federal $220 + FICA $76.50 → net $703.50. That is Pub 15 Example 3 plus Topic 751.
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$220 is what the employer remits under the flat method. Your Form 1040 uses annual income after the standard deduction or itemized deductions. State tax is out. Estimate, not tax advice.
Direct answer: $1,000 → $220 + $76.50
- Flat federal = 22% × $1,000 = $220.00
- Social Security 6.2% = $62.00
- Medicare 1.45% = $14.50
- Net = $1,000 − $220 − $76.50 = $703.50
flat FIT = 22% × amount under $1M YTD + 37% × excess FICA = 6.2% Social Security (to $184,500) + 1.45% Medicare net = bonus − FIT − FICA
Flat-method checks
| Bonus | Federal 22% | FICA | Net |
|---|---|---|---|
| $1,000 | $220.00 | $76.50 | $703.50 |
| $5,000 | $1,100.00 | $382.50 | $3,517.50 |
| $10,000 | $2,200.00 | $765.00 | $7,035.00 |
The $1 million cliff
YTD supplemental wages already $995,000, this bonus $25,000:
| Slice | Rate | Federal |
|---|---|---|
| $5,000 still under $1M | 22% | $1,100.00 |
| $20,000 excess | 37% | $7,400.00 |
| Total federal on the bonus | $8,500.00 |
FICA still applies on the $25,000 (7.65% = $1,912.50 if the Social Security wage base has room).
Aggregate method (same $1,500 bonus)
Single, biweekly, $2,000 regular wages + $1,500 bonus. Pub 15-T on $3,500 combined is $503.15. Tax on the $2,000 alone is $195.85. Extra FIT on the bonus: $307.30. That can be higher or lower than 22% of $1,500 ($330). FICA on the bonus is still $114.75.
Regular FIT on that $2,000 check is the same number as federal withholding.
What this is not
- Not a gross-up of a promised net bonus. Invert regular wages with paycheck gross-up.
- Not backup withholding. Missing TIN on a 1099 is a flat 24%: backup withholding.
- Not overtime. Hours over 40 are FLSA overtime.
Pub 15 §7 lets the employer elect 22% on separately identified supplemental wages if FIT was withheld from regular wages this year or last. No other flat percentage is allowed.
Yes. Social Security 6.2% up to the $184,500 2026 wage base, Medicare 1.45% with no cap. On $1,000 that is $76.50. See FICA.
No. It is first-look withholding. Credits, other income, and the Form 1040 tables can refund part of the $220 or ask for more.