State Tax Calendar
Montana 2025 Tax Deadline Calendar
Complete filing deadlines for Montana individual, S-Corp, partnership, and C-Corp returns.
How Montana Differs from Federal
- →Generally conforms to federal calendar — most Montana deadlines mirror IRS deadlines.
- →No separate extension form for individuals — pay your balance online by April 15 and an automatic extension to October 15 is granted.
- →Top income tax rate: 6.75% on income over $20,500. Montana has no sales tax.
- →S-Corp returns (Form CLT-4S) due March 15, with automatic extension to September 15.
2025 Montana Filing Calendar
| Date | Filing / Payment Type | Entity Type | Notes |
|---|---|---|---|
| Jan 15 | Q4 2024 Estimated Tax | Individuals / Sole Props | MT Form EST |
| Jan 31 | W-2 / 1099-NEC to State | All Employers | File with MT Dept. of Revenue |
| Mar 15 | S-Corp Return (Form PTE) | S-Corporations | Extension to Sep 15 |
| Mar 15 | Partnership Return (Form PR-1) | Partnerships | Extension to Sep 15 |
| Apr 15 | Individual Income Tax (Form 2) | Individuals | Extension to Oct 15 |
| Apr 15 | C-Corp Return (Form CLT-4) | C-Corporations | Extension to Oct 15 |
| Apr 15 | Q1 2025 Estimated Tax | Individuals / Sole Props | Same as federal |
| Jun 16 | Q2 2025 Estimated Tax | Individuals / Sole Props | Same as federal |
| Sep 15 | Q3 2025 Estimated Tax | Individuals / Sole Props | Same as federal |
| Sep 15 | Extended S-Corp / Partnership Returns | S-Corps / Partnerships | Final — no further extension |
| Oct 15 | Extended Individual Return | Individuals | Final deadline |
| Oct 15 | Extended C-Corp Return | C-Corporations | Final deadline |
| Jan 15, 2026 | Q4 2025 Estimated Tax | Individuals / Sole Props | Same as federal |
Montana-Specific Tax Rules
No Sales Tax
Montana is one of five states with no statewide sales tax — a significant compliance simplification for retail and service businesses.
Estimated Tax Penalty
Pay at least 90% of current year liability or 100% of prior year tax to avoid underpayment interest charges.
Non-Resident Withholding
Montana requires 6.75% withholding on pass-through income distributed to non-resident partners and shareholders.
Business Equipment Tax
Montana levies personal property tax on business equipment. Annual declarations are due March 1 with your county assessor.
Federal vs. Montana — Quick Comparison
| Filing Type | Federal | Montana |
|---|---|---|
| Individual Return | April 15 | April 15 (same) |
| S-Corp Return | March 15 | March 15 (same) |
| Partnership Return | March 15 | March 15 (same) |
| C-Corp Return | April 15 | April 15 (same) |
| Individual Extension | October 15 | October 15 (same) |
| S-Corp Extension | September 15 | September 15 (same) |
| W-2 / 1099-NEC to State | January 31 | January 31 (same) |
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Navigating Montana Tax Deadlines?
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