Montana Bonus Tax Calculator 2026

At the federal level, bonuses are classified as supplemental wages. Your employer can withhold at a flat 22% rate (37% on amounts over $1 million) or use the aggregate method, which combines your bonus with a regular paycheck to determine withholding. Either way, your actual tax is settled when you file your return.

In Montana, your bonus is also subject to a flat 5.9% state income tax. Since Montana uses a flat rate, the state withholding on your bonus is straightforward — every dollar of your bonus is taxed at the same state rate regardless of your income level.

Note that the Montana standard deduction ( $14,600 single / $29,200 married ) applies to your total annual income. If your regular salary already exceeds the deduction, your entire bonus is taxed at the full state rate.

Bonuses are also subject to FICA taxes: 6.2% for Social Security (up to the $176,100 wage base in 2025) and 1.45% for Medicare. If your combined salary and bonus exceed $200,000 ($250,000 married filing jointly), an additional 0.9% Medicare tax applies to the amount above the threshold.