AMENDED RETURNS
You are required to file an amended Montana tax return when information on your original return was reported incorrectly or to report changes made to your federal income tax return, including changes made by the Internal Revenue Service.
Statute of Limitations
If you determine that your Montana tax return was incorrect but the changes do not result in a change to your federal taxable income, you have five years from the original due date of the Montana tax return to file an amended return.
If the amended tax return involves a change to your federal taxable income, you will need to file an amended Montana tax return within 90 days, whether you voluntarily changed your federal taxable income or if you received notification of the change to your federal taxable income by the Internal Revenue Service. If you do not notify us within 90 days of the change to your federal taxable income, we have five years from the date that the changes become final on your federal tax return to adjust your Montana tax return to reflect these same changes.
Amend Instructions