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.

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.

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.

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 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).

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.

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

Corporate income tax goes into the state general fund.