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

Tax Rates

Montana corporate tax rates are:

Standard Rate

The standard corporate tax rate is 6.75%

Water’s Edge Election

The water’s edge election tax rate is 7%

A corporation can apply for approval to take the water’s edge election by submitting the Water’s Edge Election (Form WE-ELECT).(15-31-322, MCA)

Alternative Gross Sales

The alternative gross sales tax rate is 0.5% on sales in Montana. (15-31-122, MCA)

To qualify, a corporation must:

• Have only sales activity in Montana,
• Not own or rent real estate or tangible personal property, and
• Have annual gross sales in Montana of $100,000 or less.

Minimum Tax

The minimum corporate tax is $50

See 15-31-121, MCA for more details.

Due Dates and Extensions

Your Montana Corporate Income Tax Return (Form CIT) is due:

Calendar Year

May 15

Fiscal Year

The 15th day of the 5th month following the fiscal year end.
Example: If your tax year ends on September 30, your return is due on February 15.

If a due date falls on a weekend or holiday, it is due on the next business day.

Extension Deadlines

Montana grants all C corporations an automatic six-month extension to file a return. This means extensions are due:

Calendar Year

November 15

Fiscal Year

The 15th day of the 11th month following the fiscal year end.
Example: If your tax year ends on September 30, your return is due on August 15.

If a due date falls on a weekend or holiday, it is due on the next business day.

Federal Tax Reform—965 Income, GILTI and FDII

Montana Corporate Income Tax Treatment of International Tax Provisions under Tax Cuts and Jobs Act of 2017 (Read Online) (PDF, 515 KB)

Estimated Payments

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

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

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).

Filing and Payment Options

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

You may:

• File and pay using an approved corporate income tax software provider,
• Pay taxes using Business Tax Express,
• Make ACH Credit Payments, or
• Use the Montana Corporate Income Tax Return (Form CIT).

If you have no business activity during the tax year, you may file an Affidavit of Inactivity for Corporations, Partnerships and Disregarded Entities (Form INA-CT).

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

Penalties and Interest

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

Revenue Distribution

Corporate income tax goes into the state general fund.