(1) An original return is considered to be the return that is due on the fifteenth day of the fourth month after the close of the taxpayer's tax year.

(2) Original returns are Montana Forms 2, 2S and FID-3 only.

(3) An amended return is not an original return but only a correction to an original return.

(4) An amended return will not be accepted without an original return being on file with the department.

(5) Late file and late pay penalties are assessed as required under 15-1-216 and 15-30-321 , MCA, on the correct amount due on the original return.

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

(7) For tax years beginning January 1, 2001, the late file and 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.

(8) If required by 15-1-216 and 15-30-321 , MCA, interest will be calculated on the original return. If an amendment is made to the original return, interest will be calculated as required under 15-30-149 or 15-30-142 , MCA, as of the due date in (1) .

(9) An extension of time to file an original return does not extend the time to pay. When an original return is filed before the extension date and payment is not made, the return is subject to late pay penalties.

(10) If an extension of time to file has been made and the original return was not filed before the extension deadline, the original return is subject to late file and late pay penalties.

(11) The appeal process, provided in ARM 42.2.613 through 42.2.621, will apply to adjustments and corrections made by the department to a filed amended return.