N.D. Cent. Code § 57-20-19

Any owner of real property who has entered into an extension contract under the provisions of chapter 240 of the 1937 Session Laws, or under chapter 227 of the 1939 Session Laws, if such contract is in force, has the right to discharge the interest in full upon that person's obligation by paying interest at four percent from April 1, 1941. Any owner who has entered into such an extension contract, or that owner's successor in interest, or any lien or mortgageholder, has the right to pay the full amount remaining unpaid upon such extension contract at any time while such contract is in force.