1.    The gross production tax on oil or gas, as herein provided, must be paid on a monthly basis. The tax on oil is due and payable on the twenty-fifth day of the month succeeding the month of production. The tax on gas is due and payable on the fifteenth day of the second month succeeding the month of production. If the tax is not paid as required by this section, it becomes delinquent and must be collected as provided in this chapter. The penalty does not apply if ninety percent of the tax due has been paid with the monthly return and the taxpayer files an amended monthly return and pays the total tax due within sixty days from the original due date. The commissioner, upon request and a proper showing of the necessity therefor, may grant an extension of time, not to exceed fifteen days, for paying the tax and when the request is granted the tax is not delinquent until the extended period has expired. Any taxpayer who requests and is granted an extension of time for filing a return shall pay, with the tax, interest at the rate of twelve percent per annum from the date the tax was due to the date the tax is paid.

    2.    On oil or gas produced and sold, the gross production tax thereon must be paid by the purchaser, and the purchaser is authorized to deduct in making settlement with the producer or royalty owner, the amount of tax paid; provided, that in the event oil produced is not sold but is retained by the producer, the tax on the oil not sold must be paid by the producer, including the tax due on royalty oil not sold; provided further, that in settlement with the royalty owner the producer has the right to deduct the amount of the tax paid on royalty oil or to deduct therefrom royalty oil equivalent in value at the time the tax becomes due with the amount of the tax paid.

3.    Gas when produced and utilized in any manner, except when used for fuel or otherwise used in the operation of any lease or premises in the drilling for or production of oil or gas therefrom, or for repressuring thereon, must be considered for the purpose of this chapter, as to the amount utilized, as gas actually produced and saved.

4.    All calculations of the gross production tax on oil or gas, including production, distribution, and claims for credit or refund, are based on the month of production and must be credited to that month.