15-37-105. Computation and payment of tax. (1) The tax due under this part is computed according to 15-37-103. For the reporting periods defined in 15-37-102(2), the tax is due at the end of the reporting period, and for the reporting period ending June 30, the tax is payable by August 15, and for the reporting period ending December 31, the tax is payable by March 31. The tax is imposed on the products produced in the reporting period.

(2) If good cause is shown, the department may grant a reasonable extension of time for payment of the tax. During the period of any extension granted, the tax due bears interest as provided in 15-1-216.

(3) If a person has sold or otherwise disposed of any of the mine's products at a price substantially below the true market price of the product at the time and place of sale or disposal, then the department shall compute the gross value of the portion of the mine's product that was sold or disposed of substantially below the market price. The gross value must be based upon the quotations of the price of the mine's product in New York City at the time the portion of the product was sold or otherwise disposed of as evidenced by an established authority or market report, such as the Engineering and Mining Journal of New York, or other standard publication, giving the market reports for the reporting period covered by the statement. If there is no quotation covering a particular product, then the department shall fix the value of the gross product or portion of the gross product that was sold or otherwise disposed of at a price substantially below the true market price at the time and place of sale or disposal in a manner as may seem to be equitable.