How Idaho withholds on a bonus
Idaho's withholding guide lets employers withhold a separately paid bonus at the state's flat rate, 5.3% for 2026. On a $10,000 bonus the percentage method withholds $2,200 federal, $620 Social Security, $145 Medicare and $530 Idaho, leaving $6,505. Idaho has no local income taxes, so that is the whole state line.
Because the rate is flat, the aggregate method changes Idaho withholding only marginally; the federal line rises to about $2,700 for a $60,000 earner paid every two weeks. Idaho's zero bracket ($4,811 for a single filer) and the federal standard deduction it adopts have normally been used up by regular salary by the time a bonus is paid, so the bonus is taxed at the full 5.3% on the return and the state withholding settles close to even.
What the withholding means for your Idaho return
The refund or balance on an Idaho bonus comes from the federal side. A $60,000 single filer's marginal federal rate is 12% up to $50,400 of taxable income and 22% above, so a $10,000 bonus is really taxed at about $1,450 federal against $2,200 withheld, and roughly $750 returns. Washington residents who earn a bonus for work in Idaho are withheld for Idaho on it. The Idaho paycheck calculator shows the marginal rates for any salary. Allowances on Idaho Form ID W-4 do not reduce the flat 5.3% withheld from a separately paid bonus; they apply only under the aggregate method, where the bonus is combined with the period's regular wages.