Montana Corporate Income Tax

Any C corporation doing business in Montana has to file a Montana Corporate Income Tax Return (Form CIT) and pay a corporate income tax.

If you make a Subchapter S election at the federal level, you must also file as an S Corporation in Montana.

E-File Mandate

Corporations are required to electronically file for all tax periods beginning after December 31, 2022 (SB 24). Corporations must use an approved corporate income tax software provider to e-file their Montana Corporate Income Tax return.

E-File Mandate does not apply if:

  • A corporation has gross receipts of $750,000 or less for the tax period. This is an automatic exemption from the electronic filing requirement and Form CWR is not required.
  • A corporation attests, on Form CWR (Corporate E-file Waiver Request), that the corporation attempted to file electronically and was unsuccessful or that hardship would result by filing electronically. 

Tax Rates

Category Rate
Standard Rate 6.75%
Water's Edge Election 7%
Alternative Gross Sales 0.5%
Minimum Tax $50

Additional Notes

  • To qualify for the Alternative Gross Sales tax rate, your corporation must:
    • Have only sales activity in Montana
    • Not own or rent real estate or tangible personal property in Montana
    • Have gross sales of $100,000 or less in Montana
  • To elect Water’s Edge, submit a request through the TransAction Portal (TAP).

See 15-31-121 to 15-31-122, MCA and 15-31-322, MCA for statutory details.

Due Dates and Extensions

Below are the due dates for Montana Corporate Income Tax Return (Form CIT):

Tax Year Type Filing Due Date
Calendar Year May 15
Fiscal Year 15th day of the 5th month after year-end

Example: A fiscal year ending September 30 → due by February 15

If the deadline falls on a weekend or holiday, the return is due the next business day.

Montana grants all C corporations an automatic six-month extension to file a return.
Tax Year Type Extension Deadline
Calendar Year November 15
Fiscal Year 15th day of the 11th month after year-end

Extension Deadlines are for Returns Only

Any tax liability must still be paid by the original due date or it will be subject to uniform penalties and interest.

Estimated Payments

If your business estimates owing $5,000 or more, you will need to make quarterly estimated tax payments.

If a corporation doesn't make estimated payments, it may be subject to penalties and interest. You can calculate these using the Underpayment of Estimated Tax by Corporation (Form CIT-UT).

Estimated payments are due on the 15th of the fourth, sixth, ninth, and twelfth months of your tax year.

Example

If your tax year ends on December 31, your estimated payments are due:

Payment Due Date
1st April 15
2nd June 15
3rd September 15
4th December 15

Filing and Payment Options

You must file a Montana Corporate Income Tax Return (Form CIT) every year you do business in Montana. You may:

If you have no business activity during the tax year, you may file an Affidavit of Inactivity for Corporations, Partnerships and Disregarded Entities through TAP.

See the Montana Form CIT Corporate Income Tax Booklet for more details on filing Corporate Income Tax.

Additional Corporate Tax Information

Montana has adopted sections of the Multistate Tax Compact guidelines for determining what share of business income is reportable to Montana. Income will either be apportioned to Montana using an apportionment formula or directly allocated to Montana. See section 15-31-301 to 312, Montana Code Annotated, for more information on determining apportionable and non-apportionable income.

For tax periods beginning on or before June 30, 2021, Montana used an equally-weighted 3 factor apportionment formula consisting of property, payroll, and receipts.

For tax periods beginning after June 30, 2021, the apportionment formula has been changed to use a double-weighted receipts factor. This new formula consists of property, payroll, and the receipts factor counted twice.

See Montana Source Income for more details on apportionment and allocation of income.

For periods beginning after December 31, 2024 the apportionment formula will include only the receipts factor.

The Corporate Income Tax is subject to uniform penalties and interest.

Corporate income tax goes into the state general fund.