The penalty for late filing of Montana Form MCS (Motor Carrier Services) varies depending on the specific circumstances and the amount of time the filing is overdue. Generally, the penalty for late filing is calculated as a percentage of the total tax due. If the filing is less than 30 days late, the penalty is 5% of the tax due. If the filing is 31-90 days late, the penalty increases to 10% of the tax due. If the filing is more than 90 days late, the penalty is 20% of the tax due. It's important to note that these penalties apply to the late filing of Form MCS, and additional penalties may apply for the late payment of taxes owed. It's recommended to refer to the specific instructions provided by the Montana Department of Revenue or consult with a tax professional for accurate and up-to-date information regarding penalties for late filing of Form MCS in Montana.