Bonus Tax in Idaho (2026)
A bonus is supplemental pay, and it is usually withheld at a flat federal rate rather than your normal bracket. Employers apply 22% to supplemental wages up to a yearly threshold, and a higher rate on the part above it. FICA comes out on top, and then the Idaho state layer applies.
Worked example: a $5,000 bonus in Idaho
| Federal withholding (22%) | $1,100 |
| FICA (Social Security + Medicare) | $383 |
| Idaho withholding | $265 |
| Total withheld | $1,748 |
| You keep about | $3,252 |
Assumes year-to-date wages under the $184,500 Social Security wage base. Withholding, not final tax — it reconciles on your return.
Bonus tax calculator (2026)
| Federal withholding (flat 22%) | $1,100 |
| FICA (Social Security + Medicare) | $383 |
| Idaho withholding (5.3%) | $265 |
| You keep about | $3,252 |
Assumes your year-to-date wages are under the $184,500 Social Security wage base. Withholding, not your final tax — it reconciles on your return.
See what your regular paycheck keeps in Idaho: Idaho paycheck calculator.
Frequently asked questions
Why is my bonus taxed so high?
What you see is withholding, not your final tax. Federal rules withhold supplemental pay like a bonus at a flat 22%, which is often more than your normal rate, so the bonus looks heavily taxed. It squares up when you file, where your real rate is applied to your total income.
Does Idaho have a flat bonus withholding rate?
It depends on the state. The breakdown above shows Idaho's supplemental rate if it has one, or notes when the aggregate method applies instead.
Federal: IRS 2026 brackets (Rev. Proc. 2025-32) · FICA: IRS Topic 751 · Wage base: SSA · Idaho: Idaho State Tax Commission. Rates current as of July 16, 2026. Annual-liability estimates, not payroll withholding — see methodology.