N.D. Cent. Code § 57-39.2-30

For purposes of the tax imposed by this chapter, on any sale made under a conditional sales contract or under other forms of sale in which the payment of the principal sum is extended over a period longer than sixty days from the date of sale, only the portion of the sale amount that has actually been received in cash by the retailer during each reporting period is subject to the tax imposed by this chapter during that reporting period.