You must file an amended return if:

• You learn there is an error on your original return
• You make changes to your federal income tax return
• The IRS makes changes to your federal income tax return

Your amended Montana income tax return is due 180 days after receiving a notification of the change from the IRS or after filing your amended federal income tax return.

Amended returns may be filed by a taxpayer in Montana up to three years after the original due date.

When you file an amended return, you will need to use the same form as your original return.

Mark the box labeled "Mark this box if this is an amended return" at the top of the form and complete the Amended Return Information section at the bottom of page 2.

Include copies of all of schedules you submitted with your original return, even if none of the amounts have changed as well as all new schedules you are submitting for the first time.

If you need to amend multiple returns, please file each return separately from other returns.

If you are amending your tax return to carry back a net operating loss, mark the "NOL carryback" box Amended Return Information section at the bottom of page 2 of the Form 2 for individuals. Estates and trusts mark the "NOL carryback box on Form FID-3, Schedule H.

If your amended return results in a refund, we'll mail a check to the address included on the return. If you overpaid your tax, we'll apply interest to your refund at the same rate we charge on past-due taxes.

Learn more about Late Fees, Interest, and Penalties.

Amended Returns and Penalties

If you owe additional taxes after you amend your return, you should pay the tax and interest with your amended return. If you pay the tax and interest, we will automatically waive the late payment penalty.

We figure any late pay penalty and interest on unpaid tax from the original return's due date.

Other Important Information

• If you itemized deductions on your original return, you should recalculate to see if your income changes affect the limits on medical expenses and miscellaneous itemized deductions.
• A change to your income may also change your taxable social security benefits, partial pension and annuity income exemption, or standard deduction.
• If you are amending from filing jointly to filing separately (on the same or separate forms), include a detailed breakdown showing the income and deductions for each spouse.