Business Tax Deadlines

State filing information

Montana

Business tax filing in Montana: state returns, sales tax, other business taxes, and the federal dates that apply everywhere.

checked 2026-09-01Verified against Montana Department of Revenue. 11 sources.

Corporate income tax return

May 15
15th day of the 5th month after the close of the tax year

Partnership / S corporation returns

March 15
Partnerships March 15; Same for S corporations

Sales tax return

None
No statewide sales tax.

Other business taxes

2 taxes
Corporate income tax minimum tax ($50); Selective sales/use taxes (lodging facility use tax + lodging sales tax, rental vehicle tax, cannabis tax) and local resort taxes

Montana Department of Revenue

Other business taxes

TaxWho owes itDue
Corporate income tax minimum tax ($50)Every C corporation filing Form CITWith Form CIT, 15th day of the 5th month after year end (May 15 calendar year)
Selective sales/use taxes (lodging facility use tax + lodging sales tax, rental vehicle tax, cannabis tax) and local resort taxesOnly lodging, short-term vehicle rental, cannabis, and businesses in designated resort communities; not a general business tax–

Rules in full

Corporate income tax

15th day of the 5th month after the close of the tax year

Extension. Automatic 6-month extension to the 15th day of the 11th month after year end (Nov 15 for calendar year); payment still due by original due date

Partnerships and S corporations

Elective pass-through entity tax (SB 554, 2023) made annually on Form PTE by the extended due date; irrevocable once made. Rate 6.75% for 2023, 5.9% for 2024 and later. Quarterly PTET estimates due 15th of the 4th, 6th, 9th months and 1st month after year end (Apr 15/Jun 15/Sep 15/Jan 15); underpayment penalty and interest apply beginning tax year 2024. Composite tax and pass-through withholding are due on the original return due date regardless of extension.

Notes

Montana has no general sales tax and no franchise tax. PTET rate dropped from 6.75% (2023) to 5.9% (2024+).

What we could not confirm. Selective-tax due dates (lodging/rental vehicle) were not fetched from an official page and are left null. Annual report is a Secretary of State filing (not DOR) so it is null by design. The 2025 Form CIT instructions PDF could not be parsed; the CIT facts come from the DOR corporate-income-tax web page instead.

Active IRS disaster relief in Montana

Taxpayers in the declared areas below have federal deadlines postponed. The IRS release governs who qualifies.

  1. SEP28Mon
    Montana
    Tax relief for taxpayers in the Crow Tribe of Montana impacted by severe winter storm and straight-line winds
    Postponed to

All active postponements

Federal dates that apply in Montana

  1. SEP15Tue
    Individuals & Sole Proprietors
    Q3 2026 estimated tax payment (Form 1040-ES)
  2. SEP15Tue
    Partnerships
    Form 1065 extended return (Form 7004), tax year 2025
  3. SEP15Tue
    S-Corporations
    Form 1120-S extended return (Form 7004), tax year 2025
  4. SEP15Tue
    C-Corporations
    Q3 2026 corporate estimated tax (Form 1120-W)
  5. OCT15Thu
    Individuals & Sole Proprietors
    Form 1040 extended return (Form 4868), tax year 2025
  6. OCT15Thu
    C-Corporations
    Form 1120 extended return (Form 7004), tax year 2025

All 2026 federal deadlines

Sources

  1. https://revenue.mt.gov/ official
  2. https://revenue.mt.gov/taxes/corporate-income-tax official
  3. https://revenue.mt.gov/publications/montana-corporate-income-tax-return-form-cit official
  4. https://revenue.mt.gov/taxes/pass-through-entities/s-corporations official
  5. https://revenue.mt.gov/taxes/pass-through-entities/partnerships official
  6. https://revenue.mt.gov/taxes/pass-through-entities/pass-through-entity-tax official
  7. https://www.forvismazars.us/forsights/2023/11/montana-issues-additional-guidance-on-pass-through-entity-tax-election official
  8. https://revenue.mt.gov/taxes/general-sales-tax official
  9. https://www.filelater.com/montana/business-extension-instructions/
  10. https://www.salestaxinstitute.com/jurisdiction/montana
  11. https://taxcloud.com/sales-tax/montana/

Checked 2026-09-01; researcher confidence 0.90. Corrections with a link to the state's own page: contact@businesstaxdeadlines.com.