Idaho Bonus Tax Calculator 2026

5.3% on a separately issued payment

The State Tax Commission's guidance on computing Idaho withholding lists bonuses, commissions, overtime, accumulated sick leave, severance, awards, prizes, back pay and retroactive pay as supplemental wages and gives two ways to withhold: combine the payment with regular wages and treat it as a single payment, or "multiply the separately-issued supplemental payment by 5.3%." On a $5,000 bonus that is $265.00; on $3,000, $159.00.

Allowances no longer matter

Idaho's percentage tables (EPB00744, dated July 23, 2026) withhold 5.3% of annual wages above $16,100 for single and head-of-household employees and above $32,200 for married employees. Idaho used to let employees reduce wages by a child tax credit allowance, but that credit has sunsetted under Idaho Code § 63-3029L and the allowance is now zero. As a result, a bonus combined with regular pay for someone above those thresholds also works out to 5.3% — the two permitted methods agree.

Federal withholding is the variable that moves: with the aggregate method the same bonus nets $3,186.19 instead of $3,252.50.

When Idaho withholds at all

Idaho's income tax rules (IDAPA 35.01.01, Rule 871) require withholding only on the part of pay reasonably attributable to services performed in Idaho, allocated by workdays, hours, mileage or commissions. Pay for work done wholly outside Idaho is exempt regardless of residency, as are certain nonresident interstate transportation and air-carrier employees. A bonus for a year split between Idaho and another state is therefore withheld only on the Idaho share.