The purchaser may pay all or any installments of principal not yet due to any interest-paying date. If the purchaser so desires, the purchaser may pay the entire balance due on the contract, plus accrued interest to date of payment, at any time, and the purchaser will then be entitled to proper conveyance. Payment for school or institutional lands purchased under the provisions of chapter 15-09 may be made at any time.
N.D.C.C. § 15-06-32