Idaho Code § 42-2977
If at any time twenty per cent (20%) or more of the entire issued, uncalled and outstanding bonds of such district shall be past due and unpaid, after the application of all funds available for the payment thereof, then the numerical order, or other provisions of law, of payment of all outstanding and uncalled bonds of such district shall immediately cease, and thereafter the county treasurer shall distribute all funds coming into his hands applicable to the payment of bonds pro rata on all outstanding and uncalled bonds, whether due or to become due, to the end that after such default in the percentage herein set out, there shall be paid on each outstanding and uncalled bond its equal and ratable proportion of all funds so collected for the payment of said bonds; provided further, that if at the time of such default there shall be matured and unpaid interest on any or all of such outstanding bonds, then all moneys thereafter available for the payment of interest shall be applied toward the payment of interest longest in default until all bonds shall have assumed the same relative position in regard to interest payment. When interest shall have been paid on all outstanding bonds to the same date, thereafter all moneys available for the payment of interest shall be paid equally and ratably to the holders of all outstanding and uncalled bonds. No payment shall be made by the county treasurer after such default, upon either principal or interest, except upon presentation of the bond and the indorsement by the county treasurer of the amount paid thereon, together with the date of payment, except in the event of full payment of interest coupons, said coupons shall be surrendered to the county treasurer.
Idaho Code § 42-2977