Montana Income Tax Calculator

How to Use This Montana Income Tax Calculator

This Montana income tax calculator estimates your annual MT state and federal tax liability for 2025 and 2026. Enter your gross wages, filing status, and any pre-tax deductions above. Montana applies two brackets — 4.7% and 5.9% — to your federal taxable income (not gross wages).

For per-paycheck withholding estimates, use the Montana paycheck calculator. To compare Montana's tax burden against neighboring states, use the general income tax calculator.

Montana's Unique Tax Base — Federal Taxable Income

Montana is one of a small number of states that use federal taxable income as the base for state income tax, rather than a state-specific AGI or gross wages. This affects how Montana tax is calculated in important ways:

• Federal standard deduction is your Montana deduction: The $16,100 single / $32,200 MFJ federal standard deduction (2026) directly reduces your Montana taxable income. You do not file a separate Montana deduction form.
• Itemized deductions apply: If you itemize on your federal return, those same itemized deductions (mortgage interest, charitable contributions, etc.) reduce your Montana taxable income. The Montana benefit mirrors the federal benefit exactly.
• 401(k) and pre-tax deductions: Pre-tax contributions that reduce your federal W-2 taxable wages also reduce Montana taxable income — no separate Montana withholding adjustment needed.
• Tax-deferred income: Traditional IRA contributions (deductible on federal Schedule 1) reduce Montana taxable income by the same amount.

Practically, your Montana taxable income equals the number on federal Form 1040 Line 15.

Montana's 2024 Tax Reform — From Six Brackets to Two

Montana SB 399 (2021) transformed the state's tax structure, effective January 1, 2024:

• Old six-bracket system (pre-2024): Rates of 1%, 2%, 3%, 4%, 5%, and 6.75% applied to state-specific AGI. Montana residents had to calculate a separate Montana AGI using state-specific rules and a Montana standard deduction.
• New two-bracket system (2024+): 4.7% on the first $47,500 of federal taxable income (single), 5.9% above. Married thresholds are doubled.
• Tax base change: Switched from state AGI to federal taxable income — eliminating the need for separate Montana deduction tracking.
• Rate reduction: The top rate dropped from 6.75% to 5.9%, benefiting virtually all Montana taxpayers.

Step-by-Step Example — $80,000 Montana Single Filer (2026)

1. Gross wages: $80,000
2. Federal standard deduction: −$16,100 → federal taxable income: $63,900
3. Federal income tax: (progressive 10%–22% brackets): ≈ $8,082
4. FICA: $80,000 × 7.65% = $6,120
5. Montana taxable income = federal taxable income = $63,900
6. Montana income tax: 4.7% × $47,500 ($2,233) + 5.9% × $16,400 ($968) ≈ $3,201
7. Total taxes: $8,082 + $6,120 + $3,201 = $17,403
8. Annual net income: $80,000 − $17,403 = $62,597

Montana Capital Gains Tax and Capital Gains Credit

Montana does not offer a preferential rate for long-term capital gains — they are taxed as ordinary income at 4.7%–5.9%. However, Montana does provide a capital gains income tax credit:

• Capital gains credit: 2% of net long-term capital gains recognized by a Montana resident. This credit directly reduces your Montana tax liability. On $50,000 in capital gains, the credit is $1,000.
• Non-refundable: The credit cannot exceed your Montana tax liability for the year — any excess is not refunded.
• Effective rate on gains: The 5.9% top MT rate minus the 2% credit yields an effective 3.9% Montana rate on long-term capital gains for high earners — still higher than states with 0% capital gains rates.

How to Reduce Your Montana Annual Tax Liability

• Maximize traditional 401(k) contributions — $23,500 in 2026 ($31,000 if age 50+). Because Montana uses federal taxable income, every dollar contributed to a 401(k) reduces Montana taxable income by the same amount. At 4.7%–5.9%, maxing a 401(k) saves approximately $1,104–$1,386 in MT state tax per year.
• Itemize when beneficial — for Montana residents with significant mortgage interest, charitable giving, or medical expenses, itemizing federally automatically reduces Montana taxable income beyond the standard deduction.
• Contribute to an HSA — $4,300 (self-only) or $8,550 (family). HSA contributions above the line reduce federal AGI and therefore Montana taxable income.
• Montana college savings — contributions to the Montana Family Education Savings Program (529 plan) are deductible from Montana taxable income up to $3,000 per beneficiary per year (individual) or $6,000 (couple).

Tax Disclaimer

This calculator provides estimates for informational purposes only. It is not tax advice. Montana's tax base changed significantly in 2024 (SB 399) — verify current rates and tax base rules with the Montana Department of Revenue. Capital gains credit details and Social Security exemption thresholds may change. Federal brackets, FICA wage bases, and standard deduction amounts also change each year. Consult a qualified Montana-licensed CPA or tax professional for guidance specific to your situation.