How to pay Montana estimated taxes.

Montana collects its own estimated tax through the Montana Department of Revenue, separate from the IRS. Here’s who needs to pay, when, and how to pay online.

Do you need to pay?

You must make estimated payments if the tax you will owe for the year, after withholding and nonrefundable credits, is more than $500.

You avoid underpayment interest if each installment is at least one-fourth of the lesser of 90% of your current-year tax or 100% of your prior-year tax. To use the prior-year rule, you must have filed a full-year (not short-year) return for the prior year. Montana has no higher prior-year percentage for high earners. You do not need estimates if any of these apply: you were not required to file a Montana return last year; your prior tax year covered 12 months and your Montana tax was zero; you retired at age 62 or older by the end of last year (this applies in the year you retire and the year after); you became disabled last year or this year; or at least two-thirds of your gross income comes from farming or ranching.

If you underpay: Montana charges daily interest on underpaid estimates instead of a separate penalty, figured on Form EST-I. For 2026 estimates, it uses the interest rate in effect for 2027, the year your 2026 return is due.

For how to pick a safe amount, see how much to pay in estimated taxes.

Deadlines

Four installments due April 15, 2026, June 15, 2026, September 15, 2026, and January 15, 2027. This matches the federal schedule.

Payment	Due
1st	April 15
2nd	June 15
3rd	September 15
4th	January 15 of the next year

A date on a weekend or holiday moves to the next business day. Pay at least two business days early.

Paying Montana, step by step

What you need

Access to Montana TransAction Portal (TAP).
Your Social Security number and a copy of last year's Montana return.
Your bank routing and account numbers.

Start at Montana TransAction Portal (TAP), Montana's official payment site.

Go to TAP at tap.dor.mt.gov.
Under Quick Links, select Make a Payment. You can also log in to your TAP account and pay from there.
Choose individual income tax and the estimated payment type for tax year 2026, and enter your identifying information.
Enter the amount and your payment details.
Submit and save your confirmation.

Other ways to pay: Mail a check with the Montana Individual Income Tax Payment Voucher (Form IT), available on the department's forms page.

Montana will not fill these payments in for you. Your preparer has to enter each estimated payment on your Montana return. Keep your own record of the date, amount, and confirmation number.

Extension payments

You get an automatic six-month extension to file and do not file a form. An extension does not give you more time to pay. If you expect to owe, make an extension payment by April 15 through TAP or with Form IT to limit penalties and interest.

Make this year's first estimated payment as a separate transaction, marked as an estimate for the current year.

Good to know

Montana charges interest on underpaid estimates at the rate in effect for the year the return is due. For 2026 estimates, that means the 2027 rate.
If you use the annualized income method for uneven income, you must indicate it on your return to avoid interest.
Retirees age 62 or older can skip estimates in the year they retire and the following year.
Montana has no local income taxes.
Moved this year? You may owe estimates to both Montana and your other state for the part of the year you lived or earned income in each.
Paying the IRS too? Follow the federal walkthrough. Other states each have a guide of their own.

Official sources

Checked October 2026 against the Montana Department of Revenue's own publications.

This guide is for general education and reflects rules as of October 2026. Tax law and agency websites change, and your situation may have details that change the answer. Please talk with your tax professional before acting on it.