Idaho Code § 43-615

Any taxes levied for the payment of refunding bonds issued under the provisions of this act, except taxes levied for the emergency fund, may be paid in matured coupons or matured or unmatured bonds for the payment of which such taxes were levied, and the unpaid portion of any benefits apportioned or assessed against any parcel or tract of land, with interest thereon to the next interest paying date on such refunding bonds, may be paid, without any tax having first been levied for the payment thereof, to the treasurer of the district either in lawful money of the United States or by surrendering for cancellation such matured coupons or matured or unmatured bonds, which shall be accepted at their par or face value and when so received such coupons and bonds shall be cancelled.