Montana S Corporation Tax Deadlines 2026
Complete guide to S Corporation filing dates, extensions, estimated payment schedules, and required forms in Montana for the 2026 tax year. Montana imposes a state income tax, so S Corporation entities must file both federal and state returns.
Montana S Corporation filing deadline
Calendar-year due date follows federal timing for pass-through entities.
Due: Mar 16, 2026
Extension: Sep 15, 2026
Form: State business income tax return
Estimated payments
No state estimated payment schedule listed.
Due: N/A
Montana S Corporation Tax Calendar at a Glance
| Event | Date |
|---|---|
| Filing deadline | Mar 16, 2026 |
| Extension deadline | Sep 15, 2026 |
FAQ
When is the S Corporation tax filing deadline in Montana for 2026?
The Montana S Corporation tax return is due Mar 16, 2026 for the 2026 tax year. An extension is available until Sep 15, 2026.
Does Montana require S Corporation estimated tax payments?
Estimated payments are not typically required at the entity level for S Corporation in Montana, but confirm with Montana Department of Revenue.
What form do I file for a S Corporation in Montana?
S Corporation entities in Montana file using Form State business income tax return. You can download the form from Montana Department of Revenue at https://mtrevenue.gov.
Can I get an extension for my Montana S Corporation tax return?
Yes. Montana allows an extension for S Corporation returns until Sep 15, 2026. Note that an extension gives you more time to file, not more time to pay — any tax owed is still due by the original deadline of Mar 16, 2026.
What are the penalties for filing late in Montana?
Montana typically charges a failure-to-file penalty (usually 5% of unpaid tax per month, up to 25%) and a failure-to-pay penalty (usually 0.5-1% per month). Interest also accrues on unpaid balances. Filing for an extension by the original deadline avoids the failure-to-file penalty but not the failure-to-pay penalty.
Where can I file Montana S Corporation taxes?
File through Montana Department of Revenue. Visit https://mtrevenue.gov for e-filing options, downloadable forms, and payment portals.
Montana Estimated Tax Payments
View the full quarterly estimated payment schedule for Montana, including all entity types and payment methods.
View Montana estimated payments →