Montana calendar and forms

Montana keeps its income tax calendar on the federal dates. Form 2 is due April 15, 2027, the same day as the federal return; the four estimated payments fall on the federal dates; and the automatic six-month extension runs to October 15, 2027, with no form to file. The extension is to file, not to pay: tax unpaid on April 15 draws a 0.5%-a-month penalty and 7% interest from that day, extension or not. Two Montana dates are not federal at all and are easy to miss. Property tax is due in halves on November 30, 2026 and May 31, 2027, and the 2026 Property Tax Refund, for homes that did not get the homestead rate, can be requested only between January 1 and May 31, 2027.

The forms are simpler than they look. There is one return, Form 2, and since the 2024 redesign the schedules and worksheets sit inside it rather than as separate forms. Most Montana filers touch three pieces: the first page, Schedule I for additions and subtractions, and Schedule III for credits. The rest of the list below is for people who moved, who work across the state line, who owe estimated tax, or who are claiming the senior credit without filing a full return.

The 2027 filing season, dated

How the extension really works

The Department grants every individual an automatic six-month extension of time to file, with no request and no form. What it does not grant is time to pay. Anyone expecting to owe should send the expected balance by April 15, either in TAP or by check with Form IT, the payment voucher, with the “tax due with return or extension payment” box marked. From April 15 the late-payment penalty runs at 0.5% a month on whatever is unpaid, to a maximum of 12%, and interest runs at the 2026 rate of 7% a year, figured daily; the 2027 rate is to come. File by October 15 and there is no late-filing penalty at all. Miss October 15 and the late-filing penalty is the greater of $50 or 5% of the unpaid tax for each month, up to 25%, on top of the rest.

Estimated payments

Montana requires estimated payments when the tax expected for the year, after withholding and nonrefundable credits, is more than $500. The safe harbor is the lesser of two figures, paid in four equal installments: 100% of the 2025 Montana tax (Form 2 line 10), or 90% of the 2026 tax. There is no 110% tier for higher incomes. The prior-year method is open only to someone who filed a 2025 Montana return for a full twelve months. Three groups are excused even when they owe more than $500: anyone who retired and was 62 or older at the end of the prior year, for the year of retirement and the one after; anyone who became disabled in the prior or current year; and anyone with two-thirds of gross income from farming or ranching. Income that comes unevenly through the year can be annualized on Worksheet ESA inside Publication 1 to lower an early installment.

Interest on an underpayment is figured daily from each due date at 7% for 2026, and the Department computes it automatically, so Form EST-I is optional unless the filer wants to work it out. Payments go through TAP, through tax software, or by check with Form IT to PO Box 6309, Helena, MT 59604-6309. Any payment of $50,000 or more must be made electronically. Because Montana taxes pensions, IRA withdrawals and the taxable part of Social Security, the people most often caught are retirees in their first year without wage withholding, along with the self-employed, landlords and anyone with a large capital gain or a Roth conversion.

The forms, in the order a filer meets them

Filing, paying and checking a refund

Montana returns may be filed electronically or on paper; the Department states no e-file requirement for individuals (verify). Free electronic filing is through the Free File Alliance partners listed on the Department’s filing-options page, each with its own income or age limits, and anyone who does not qualify uses approved commercial software, which may charge for the state return. Montana was not an IRS Direct File state and the Department’s page does not mention it. TAP, the Department’s TransAction Portal at tap.dor.mt.gov, does not file Form 2; it files Schedule 2EC alone for seniors with no other filing requirement, takes payments by e-check or card, shows estimated payments already made, and runs Where’s My Refund. A paper return with a refund or no payment goes to PO Box 6577, Helena, MT 59604-6577; with a payment, to PO Box 6308, Helena, MT 59604-6308; estimated payments to PO Box 6309.

Where’s My Refund in TAP needs the filing status, Social Security number and expected refund amount, and updates each weeknight. An e-filed return shows up about two weeks after filing; a paper return about 18 weeks after. The Department says a refund can take up to 90 days, and asks that anyone past 90 days call (406) 444-6900. Two Montana rules surprise newcomers. A first-time Montana filer receives a paper check, not a direct deposit, as a fraud safeguard. And an identity-verification letter stops the refund until it is answered, so a letter from the Department in February is not junk mail. A refund that is smaller than expected may have been offset against a debt to a state or local agency; the Department cannot release an offset, and the agency that requested it must.