N.D. Cent. Code § 61-35-73: Lien between vendor and vendee of special assessments

As between a vendor and vendee of real property, unless the purchase contract otherwise provides, the installments of all special assessments for local improvements which are required to be certified and returned to the county auditor in each year become a lien upon the real property upon which they are assessed from and after the first day of December in that year.