Montana Capital Gains Tax Calculator
Montana taxes capital gains as ordinary income at the state level, which means a gain on selling shares, property or other investments is added to your other income and taxed using the Montana income tax brackets, with no separate preferential long-term rate like the federal system provides. This calculator estimates the Montana state tax on a capital gain by stacking the gain on top of your other taxable income and applying the sourced Montana Department of Revenue brackets for tax year 2025, then taking the difference. Enter your gain, your other annual taxable income and your filing status to see the state tax attributable to the gain and the effective rate on it. The result is the Montana state portion only; federal capital gains tax, which has separate short-term and long-term rates set by the IRS, is calculated separately. Because the gain stacks on your other income, the same gain is taxed at a higher rate the more you already earn. Some states provide specific exclusions or preferential treatment for certain gains; this tool uses the standard ordinary-income method and links the Montana Department of Revenue so you can confirm any special rule that applies to you.
Montana taxes capital gains as ordinary income. A $20,000.00 gain on top of $60,000.00 of other income (single) adds about $980.00 in Montana state tax, an effective rate on the gain of 4.90%.
How Montana taxes capital gains
Montana taxes capital gains as ordinary income, so the gain is added to your other income and taxed at the Montana bracket rates.
state tax on gain = state income tax on (other income + gain) - state income tax on (other income)
effective rate on gain = state tax on gain / gain x 100
Montana capital gains tax: frequently asked questions
How are capital gains taxed in Montana?
Montana taxes capital gains as ordinary income at the state level: the gain is added to your other taxable income and taxed using the Montana income tax brackets published by the Montana Department of Revenue. This calculator applies those brackets to your gain. Some states provide specific exclusions or rates for particular gains; confirm your situation with the Montana Department of Revenue.
How much state tax will I pay on a $20,000.00 capital gain in Montana?
Stacked on $60,000.00 of other income, a $20,000.00 gain adds about $980.00 of Montana state income tax for a single filer, an effective rate on the gain of 4.90%. Your figure depends on your total income and filing status; enter them above.
Does Montana have a separate long-term capital gains rate?
Most states, including the default treatment here, tax long-term and short-term capital gains at the same ordinary income rates, unlike the federal system which has preferential long-term rates. Any state-specific exclusion or preferential rate is set by the Montana Department of Revenue; this calculator uses the ordinary income method and links the source.
What is Montana's state income tax rate for 2025?
Montana's flat income tax rate is 4.9% for tax year 2025. This rate was established by Montana SB 399 (2023) and took effect January 1, 2024, replacing a graduated rate structure that previously topped out at 6.75%. The rate is codified at MCA §15-30-2103.
How does Montana's standard deduction work?
Montana allows a standard deduction equal to 20% of your gross income, up to an annually adjusted maximum. For 2024, the approximate maximums are $5,600 for single and married filing separately filers, and $11,200 for married filing jointly and head of household filers. Because these maximums are inflation-adjusted each year, confirm the current amounts with the Montana Department of Revenue at mtrevenue.gov.
When did Montana switch to a flat income tax?
Montana adopted a flat income tax rate of 4.9% effective January 1, 2024, under SB 399 passed by the 2023 Montana Legislature. Before that change, Montana used a graduated rate structure with multiple brackets and a top marginal rate of 6.75%.
Does Montana allow federal tax deductions on state returns?
Montana previously allowed a deduction for federal income taxes paid, which was a notable feature of the Montana return. As part of the 2023 tax reform (SB 399), this deduction was eliminated effective January 1, 2024, coinciding with the shift to the flat rate. Check the Montana Department of Revenue for current deduction rules.
Official sources
- Montana income tax rates applied to capital gains (tax year 2025): Montana Department of Revenue, as at Jun 12, 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. General information, not financial or tax advice. State-specific exclusions, if any, are set by the Montana Department of Revenue.