(1) Whenever a deficiency assessment is made by the department pursuant to 15-31-503, MCA, based on the original return, the tax becomes final as provided in 15-31-503, MCA, and the payment for the deficiency is due within 30 days as stated on the notice of deficiency assessment. If the payment is not made by the end of this period, the taxpayer is subject to imposition of a penalty as provided in 15-1-216, MCA.

(2) Amended returns will not change the calculation of the late file penalties on the original return for tax years beginning before January 1, 2001.

(3) Late pay penalties will be adjusted based on the corrected amount of tax due, which results from an amended return, adjustment from an audit, or correction to the original return.

(4) The department will adjust interest based on the corrected amount of tax due, which results from an amended return, adjustment from an audit, or correction to the original return, unless the change in tax due arises from a net operating loss or a tax credit.

(5) When there is a change to the tax liability which results from an amended return, adjustment from an audit, or correction to the original return, no change will be made to the underpayment interest penalty as calculated on the original return.

(6) A penalty assessment may be appealed by the taxpayer under the provisions of ARM 42.2.613 through 42.2.621.