CIT-UT: Underpayment of Estimated Tax by a Corporation (Form CIT-UT) (2025)

Who files this form

Form CIT-UT is used by corporations to figure underpayments of Montana estimated tax and the interest owed for tax year 2025.

• If your Montana tax liability minus credits is less than $5,000, you do not need to complete the rest of the form and do not owe underpayment interest.
• If that amount is $5,000 or more and you did not pay enough estimated tax by an installment due date, you may owe interest. Complete Part I to check for underpayments and Part II to calculate interest.
• If you have to pay underpayment interest, include Form CIT-UT with your Montana Corporate Income Tax Return, Form CIT.

If you do not want to calculate the interest yourself, the department will calculate it and send you a notice of the amount due.

When it's due

For tax year 2025, estimated tax installments are due on the 15th day of the fourth, sixth, ninth, and twelfth months of your tax year.

For a calendar-year corporation whose 2025 tax year ends December 31, the installment due dates are:

• April 15, 2025
• June 15, 2025
• September 15, 2025
• December 15, 2025

For a short tax year covered by this 2025 form, all installments must be made by the 15th day of the last month of the short tax year.

The text does not state a separate filing deadline for Form CIT-UT.

What you'll need

Have these forms and amounts available:

• Your 2025 Form CIT, including tax liability on page 3, line 10, and credits on page 4, line 13.
• Your previous year's Form CIT, if you use the prior-year tax liability to calculate required installments.
• Estimated tax payment amounts and payment dates, plus any prior-year overpayment applied to estimated tax.
• Any mineral royalty tax or tax on pass-through entities withheld on your behalf, from Form CIT lines 12d and 12e.

If you use the annualized income or adjusted seasonal method, you also need taxable income and credit amounts for the worksheet periods. The seasonal method uses income information from the three preceding tax years.

When using either worksheet method, include the completed worksheet and federal Form 2220 with your Montana return and Form CIT-UT.

How to file

1. Complete Part I to determine whether any quarterly installment was underpaid.
2. If line 13 shows an underpayment in any column, complete Part II to calculate interest.
3. Enter total interest from line 18 on Form CIT, page 4, line 18.
4. If you owe underpayment interest, include Form CIT-UT with your Form CIT. If you use the annualized or seasonal worksheet, also include that worksheet and federal Form 2220.

The mailing address printed on the form is:

Montana Department of Revenue

PO Box 8021

Helena, MT 59604-8021

The supplied text does not provide e-filing instructions.

Common mistakes

• Assuming a refund means no interest is due. Interest is calculated separately for each installment. You may owe interest for an earlier underpayment even if later payments make up the difference or you request a refund.
• Using prior-year tax when it is not allowed. If the prior return showed no tax liability, covered less than 12 months, or this is your initial return, base installments on 80% of the current year's tax liability instead.
• Completing the main form across rows instead of by column. Complete lines 7 through 14 for one column before moving to the next column.
• Changing worksheet methods between quarters. You must use the same method of determining required installments for each quarter.
• Leaving out worksheet attachments. If you use the annualized or seasonal method, mark the box on line 6 and include the worksheet and federal Form 2220.

Questions people ask

How much estimated tax should the corporation have paid?

Generally, the lesser of 80% of the current year's tax liability or 100% of the previous year's tax liability. If the prior return showed no tax liability, covered less than 12 months, or this is your initial return, use 80% of the current year's liability.

What interest rates apply?

The instructions list an underpayment interest rate of 11% for 2025 and 10.25% for 2026. Line 17 calculates interest using the underpayment, the number of days late, and the applicable rate, divided by 365.

Can uneven income reduce my required installments?

If you can establish that income was not earned evenly during the year, the annualized income or adjusted seasonal worksheet may lower one or more required installments and reduce or eliminate interest for those periods. To use the adjusted seasonal method, your base period percentage for any six consecutive months must be at least 70%.

Where can I get help?

Call (406) 444-6900, or Montana Relay at 711 for the hearing impaired.

Official sources

• https://revenuefiles.mt.gov/files/Forms/Underpayment-of-Estimated-Tax-by-a-Corporation-Form-CIT-UT/2025-Underpayment-of-Estimated-Tax-by-a-Corporation-Form-CIT-UT.pdf