Montana Personal Tax Extension Guide

Form IT  ·  Individual Income Tax  ·  Personal Filing Guide

Montana provides an automatic six-month extension for filing personal income tax returns. Taxpayers who cannot file by April 15, 2026, are automatically extended until October 15, 2026. No federal extension or separate application is required, but taxpayers must meet Montana's payment threshold to avoid late payment penalties.

To avoid late payment penalties, Montana requires one of the following to be paid by April 15, 2026:

• At least 90% of the current year's outstanding tax liability, or
• 100% of the prior year's tax liability

Use whichever option results in a lower payment to maximize flexibility.

• Online (TAP): Use the TransAction Portal at tap.dor.mt.gov. A fee applies when paying with a credit or debit card.

Form IT (Montana Individual Income Tax Payment Voucher) is used for mailing extension payments:
Montana Department of Revenue
P.O. Box 6309
Helena, MT 59604-6309

Montana's failure-to-file penalty is the lesser of $50 or the amount of tax due—one of the most modest filing penalties in the country. The failure-to-pay penalty is 1.2% of unpaid tax per month, up to a maximum of 12%. Paying the required amount by April 15 avoids the payment penalty entirely.

• Pay by April 15, 2026, using either the 90% current-year or 100% prior-year safe harbor to avoid late payment penalties.
• Use the TAP portal at tap.dor.mt.gov for online payments.
• No federal extension or state application is needed—Montana's extension is automatic.
• File your completed Montana return by October 15, 2026.

Montana's automatic extension requires no paperwork. Just pay 90% of your current year tax (or 100% of prior year's) by April 15 and file your return by October 15, 2026.

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