If you earn 1099 or self-employment income in Montana, the IRS and the state both expect you to pay taxes as you go, in four quarterly installments rather than one April bill. This calculator estimates your 2026 quarterly payments across all three pieces: federal self-employment tax, federal income tax, and Montana state income tax. Montana taxes long-term capital gains at separate, lower rates (3.0% and 4.1%) instead of the ordinary income rates. Enter your expected net self-employment income, any W-2 wages, and your filing status to see what to send each quarter, your due dates, and how the safe-harbor rules protect you from an underpayment penalty. Everything is an estimate for planning. Always confirm with the Montana Department of Revenue before you file.
Self-employment income has no tax withheld for you, so both the IRS and Montana Department of Revenue ask you to prepay in quarterly installments. On the federal side you owe self-employment tax (15.3% Social Security and Medicare on 92.35% of your net profit, up to the Social Security wage base) plus federal income tax on your profit after the standard deduction. On top of that, Montana applies its own income tax.
Montana generally requires estimated payments once you expect to owe more than $500 in state tax for the year. Montana follows the federal schedule: April 15, June 15, September 15, and January 15. If a due date falls on a weekend or holiday, it moves to the next business day. Montana follows the standard four-installment schedule.
You avoid an IRS underpayment penalty by hitting a "safe harbor": paying at least 90% of this year's total tax, or 100% of last year's (110% if your income is higher). Montana starts from your federal taxable income (so the federal standard deduction is already baked in; there is no separate Montana deduction to subtract) and applies a two-rate schedule: 4.7% up to $47,500 (single) or $95,000 (married), and 5.65% above. The top rate is scheduled to fall to 5.4% in 2027. Long-term capital gains are taxed at separate, lower rates (3.0% / 4.1%), not the ordinary rates shown here. You can pay online through the Montana Department of Revenue portal, and the calculator above breaks your total into the federal and Montana pieces so you can send each to the right place. You can pay online at the Montana Department of Revenue (payment portal).
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For educational purposes only, not tax advice. Tax rules change and individual situations vary; confirm figures with a tax professional and the Montana Department of Revenue before filing. State tax data last verified 2026-07-06.
Sources: mtrevenue.gov, mtrevenue.gov.