N.D. Cent. Code § 15.1-29-04
If the board of a school district agrees to pay tuition under this chapter, if it is required to pay tuition under this chapter, or if it is required to pay tuition and transportation under this chapter, the board of the sending district shall pay at least fifty percent of the annual charge to the admitting district on or before December thirty-first and any remaining amount on or before May thirty-first. If payment is not received by the admitting district within thirty days after the date on which payment is due, simple interest at the rate of six percent per annum accrues to any amount due. If payment is not received by the admitting district within sixty days after the date on which payment is due, the admitting district shall notify the superintendent of public instruction.
N.D.C.C. § 15.1-29-04