Whenever the amount in the hands of the treasurer, belonging to the funds set aside to pay bonds, is sufficient to redeem one or more of the bonds which by their terms are subject to redemption, the treasurer shall give the owner of said bonds thirty days' written notice of the readiness of the district to pay and the amount it desires to pay. If not presented for payment or redemption within thirty days after the date of such notice, the interest on such bonds shall cease and the amount due thereon shall be set aside for its payment whenever it is presented.
Iowa Code § 298.23