Montana tax deadlines in 2026: filing dates and estimated payments
Deadlines that fall in calendar 2026: the 2025 return and the 2026 estimated payments. Different year? See Montana 2025 →
Montana deadlines in 2026
| 2025 individual return due | April 15, 2026 |
|---|---|
| Extended filing deadline | October 15, 2026 |
| Payment due | April 15, 2026, extension or not |
| Final 2025 estimated payment | January 15, 2026 |
| 2026 estimated payments | April 15, 2026 · June 15, 2026 · September 15, 2026 · January 15, 2027 |
Conforms to the federal deadline; automatic 6-month extension to October 15.
Montana estimated tax payments in 2026
You must make estimated payments when the annual estimated tax you owe, after withholding and nonrefundable credits, is more than $500.
| Q1 (2026 tax year) | April 15, 2026 |
|---|---|
| Q2 (2026 tax year) | June 15, 2026 |
| Q3 (2026 tax year) | September 15, 2026 |
| Q4 (2026 tax year) | January 15, 2027 |
| Voucher | Worksheet ESW (Montana Estimated Tax, in Publication 1); mailed payments use the individual income tax payment voucher |
| Underpayment safe harbor | Each installment is the lesser of one-fourth of the prior-year tax (full-year prior return required) or one-fourth of 90 percent of the current-year tax. |
| Pay online | tap.dor.mt.gov |
No estimates are required if you were not required to file a Montana return the prior year, your prior 12-month year had zero Montana liability, you retired at age 62 or older (year of retirement plus one more year), you became disabled in the prior or current year, or at least two-thirds of your gross income is from farming and ranching.
Source: revenuefiles.mt.gov, read September 3, 2026. “For taxpayers with a tax year beginning on January 1, estimated tax payments are due April 15, June 15, and September 15 of that year, and January 15 of the next calendar year.”
All 51 jurisdictions in one table: state estimated tax payment dates for 2026.
Montana extensions
Every state's rule in one table: which states accept the federal extension in 2026.
| Does Montana accept the federal extension? | Not needed. The state extends everyone automatically. |
|---|---|
| Original due date | April 15, 2026 |
| Extended due date | October 15, 2026 |
| Payment | Still due April 15, 2026. The extension is to file, not to pay. Extensions are for filing only; tax must be paid by the due date to avoid penalties and interest. |
| How to get it | Nothing to file; make any extension payment through the TransAction Portal (TAP) or with the Montana Individual Income Tax Payment Voucher (Form IT). |
Montana's extension does not depend on the federal Form 4868; everyone gets six months.
Source: mtrevenue.gov, read September 3, 2026. “You receive an automatic six-month extension to file your individual income tax return. You do not need to submit a form for the extension.”
Federal deadlines in 2026
| 2025 Form 1040 | April 15, 2026 · extension October 15, 2026 |
|---|---|
| 2025 S-corp (1120-S) & partnership (1065) | March 16, 2026 |
| 2025 C-corp (Form 1120) | April 15, 2026 |
| 2026 federal estimated payments (1040-ES) | April 15, 2026 · June 15, 2026 · September 15, 2026 · January 15, 2027 |
Source: IRS Publication 509 and Form 1040-ES instructions, irs.gov.
Frequently asked questions
When are Montana state taxes due in 2026?
Your 2025 Montana individual income tax return is due April 15, 2026. If that date falls on a weekend or legal holiday, the deadline moves to the next business day. An extension moves the filing deadline to October 15, 2026, but any tax owed is still due on the original date.
When are Montana estimated tax payments due in 2026?
Montana estimated payments for the 2026 tax year are due April 15, 2026, June 15, 2026, September 15, 2026, January 15, 2027. Use Worksheet ESW (Montana Estimated Tax, in Publication 1); mailed payments use the individual income tax payment voucher or pay online. The final installment for 2025 was due January 15, 2026.
Does Montana accept the federal extension?
Not needed. The state extends everyone automatically. The extended filing deadline is October 15, 2026, and tax is still due by April 15, 2026.
Does a Montana extension give me more time to pay?
No. An extension extends the time to file, not to pay. To avoid penalties and interest, pay what you expect to owe by April 15, 2026.
Dates are the statutory deadlines that fall in 2026 and move to the next business day when they land on a weekend or holiday. Each section links to the source it was checked against. Always confirm with the Montana tax agency or the IRS before relying on a date. This is general information, not tax advice.