1.    The commissioner may ascertain and determine whether a return required to be filed with the commissioner is a true and correct return of the gross products, and of the value thereof, of that person. If any person has made an untrue or incorrect return of the gross production or value thereof, as hereinbefore required, or has failed or refused to make a return, the commissioner shall under rules adopted by the commissioner, ascertain the correct amount of either, and compute the tax.

2.    The time to assess additional tax found due is three years after the due date of the original return or three years after the original return is filed, whichever period expires later. However, if there is a change in tax liability on any return by an amount in excess of twenty-five percent of the amount of tax liability reported on a return, any additional tax determined to be due may be assessed anytime within six years after the due date of the return or six years after the return was filed, whichever period expired later.

3.    If a taxpayer files an amended return, the tax commissioner has two years after the return is filed to audit the return and assess any additional tax attributable to the changes or corrections even though other time periods prescribed in this section for the assessment of tax may have expired. The provisions of this section do not limit or restrict any other time period prescribed in this section for the assessment of tax that has not expired as of the end of the two-year period prescribed in this section.

4.    For periods in which the tax commissioner has waived the requirement that a producer file a well production report required under section 57-51-06, the tax commissioner has three years after the due date of the purchaser’s return or three years after the purchaser’s return is filed, whichever period expires later, to assess the producer for additional tax found due. However, if there is a change in tax liability on the purchaser’s return by an amount in excess of twenty-five percent of the amount of tax liability reported on a purchaser’s return, any additional tax determined to be due may be assessed from the producer anytime within six years after the due date of the purchaser’s return or six years after the purchaser’s return was filed, whichever period expires later.

5.    Any person who consents to an extension of time for assessment of tax must be presumed to have consented to a similar extension for refund.