Montana State Tax Guide
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Montana State Tax Guide
Montana Key deadlines (tax year 2025, return filed in 2026)
- Filing deadline: Apr 15, 2026
- Extension request deadline: Apr 15, 2026 — Automatic unless you owe a tax liability then the deadline to file is April 15, 2026
- Extended return deadline: Oct 15, 2026 (6-month extension)
- Payment deadline: Apr 15, 2026
- Differs from federal: No
You must pay your estimated tax liability by the original April deadline. Montana requires you to pay either 90% of your current year's tax liability or 100% of your previous year's tax liability by the original due date
If the due date for filing your return falls on a Saturday, Sunday, or legal holiday, your return is due by the next regular working day.
October 15, 2026 (6-month extension)
Payment rules
You must pay your estimated tax liability by the original April deadline. Montana requires you to pay either 90% of your current year's tax liability or 100% of your previous year's tax liability by the original due date
Payment options
Montana Refund Tracking
Do I need to file?
Not unless you owe a balance
Filing methods
Online filing
You may make an extension payment: • Through our Montana TAP
Mail filing
You may make an extension payment: Using the Form Montana Individual Income Tax Payment Voucher
