Section 78-C:4 - Payment of TaxI. One-third of the taxpayer's estimated tax on refined petroleum products for the subsequent taxable period is due and payable at the time the taxpayer files the declaration required in RSA 78-C:3, II; 1/3 is due and payable one month thereafter; and 1/3 is due and payable 2 months thereafter. If the return required by RSA 78-C:3, I, shows an additional amount to be due, such additional amount is due and payable at the time the return is filed. If such return shows an overpayment of the tax due, the commissioner shall allow the taxpayer a credit against a subsequent payment or payments due, to the extent of the overpayment.II. Any person who produces refined petroleum products who fails to make payment when due shall, in addition, pay a late payment charge equal to 10 percent of the defaulted payment plus interest computed at the rate of one percent per month or fraction thereof from the prescribed payment date to the date payment is actually made. Such late payment charge and interest shall be in addition to any late filing fee which may be due under the provisions of RSA 78-C:3, III.1974, 39:4, eff. April 5, 1974.