N.D. Cent. Code § 57-06-25
Taxes under section 57-06-17.3 are due January first for the preceding taxable year and are delinquent if not received by the commissioner by March first following the due date. If any amount of tax imposed by this chapter is not paid on or before March first, or if upon an additional audit additional tax is found to be due, there must be added to the tax due a penalty at the rate of one percent of the tax due for each month or fraction of a month during the first year during which the tax remains unpaid, computed from March first. Beginning on January first of the year following the year in which the taxes become due and payable, simple interest at the rate of twelve percent per annum upon the principal of the unpaid taxes must be charged until the taxes and penalties are paid, with the interest charges to be prorated to the nearest full month for a fractional year of delinquency.
N.D.C.C. § 57-06-25