Bonus Withholding Formulas and How They Work
The calculation applies flat rates to your gross bonus for each tax component separately:
Federal Withheld = Bonus Amount x (Federal Rate / 100)
State Withheld = Bonus Amount x (State Rate / 100)
FICA Withheld = Bonus Amount x (FICA Rate / 100)
Total Withheld = Federal + State + FICA
Net Bonus = Bonus Amount - Total Withheld
Effective Rate = (Total Withheld / Bonus Amount) x 100
For a $10,000 bonus at 22% / 5% / 7.65%: Federal = $2,200, State = $500, FICA = $765, Total = $3,465, Net = $6,535, Effective Rate = 34.65%.
Withholding Comparison by Scenario
| Scenario | Bonus | Federal | State | FICA | Total Withheld | Net Pay | Effective Rate |
|---|---|---|---|---|---|---|---|
| Standard (22/5/7.65) | $10,000 | $2,200 | $500 | $765 | $3,465 | $6,535 | 34.65% |
| No State Tax (22/0/7.65) | $10,000 | $2,200 | $0 | $765 | $2,965 | $7,035 | 29.65% |
| High State - CA (22/9.3/7.65) | $10,000 | $2,200 | $930 | $765 | $3,895 | $6,105 | 38.95% |
| High Earner (37/5/7.65) | $10,000 | $3,700 | $500 | $765 | $4,965 | $5,035 | 49.65% |
| Large Bonus (22/5/7.65) | $25,000 | $5,500 | $1,250 | $1,912.50 | $8,662.50 | $16,337.50 | 34.65% |
Percentage Method vs. Aggregate Method
The IRS provides two approaches for withholding on supplemental wages like bonuses.
The percentage method applies a flat 22% federal rate (37% for amounts over $1 million) directly to the bonus, which is what this calculator models.
The aggregate method combines the bonus with your regular paycheck for that period and withholds as though the combined amount is a single regular payment — this can result in higher withholding if the combined amount pushes into higher bracket ranges.
Most employers use the percentage method for distinct bonus payments because it is simpler to administer.
Either way, your actual tax liability is reconciled on your Form 1040 at filing time.
If more was withheld than you owe, you receive a refund; if less was withheld, you owe the difference.
