Mont. Code Ann. § 15-30-3408

A taxpayer may make estimated payments to the department, following the process prescribed by the department, of the Montana individual income or corporate income tax expected to result from a pending internal revenue service audit, prior to the due date of the federal adjustments report, without having to file the report with the department. The estimated tax payments must be credited against any tax liability ultimately found to be due to this state and will limit the accrual of further statutory interest on that amount. If the estimated tax payments exceed the final tax liability and statutory interest ultimately determined to be due, the taxpayer is entitled to a refund or credit for the excess, provided the taxpayer files a federal adjustments report or claim for refund or credit of tax pursuant to 15-30-2609 or 15-31-509, no later than 1 year following the final determination date.