You're granted an automatic, six-month extension of time for filing your Montana income tax return. You do not have to apply for a federal extension in order to receive a Montana extension.
If you're required to make an extension payment, please use the Montana Form IT , 2018 Individual Income Tax Payment Voucher.
Any extension of time to file your Montana income tax return is not an extension of time to pay your income tax liability. If you have a valid Montana extension but you haven't paid your entire 2018 income tax liability by April 15, 2019, you're relieved of late filing penalties but you aren't relieved of late payment penalties and interest on your outstanding Montana income tax liability.