In all cases where bonds are issued to pay the cost and expense of a local improvement, the ordinance levying the assessments shall provide that the sum charged against any lot, tract, and parcel of land, or other property, or any portion thereof, may be paid during the 30-day period allowed for the payment of assessments without penalty or interest and that thereafter the sum remaining unpaid may be paid in equal annual installments. The number of installments shall be less by two than the number of years which the bonds issued to pay for the improvement are to run. Interest on the whole amount unpaid at the rate fixed by the ordinance shall be due on the due date of the first installment of principal and each year thereafter on the due date of each installment of principal. The first installment shall become due and payable during the 30-day period succeeding a date one year after the date of first publication of the treasurer’s notice, as provided in LMC 3.28.090, and annually thereafter each succeeding installment shall become due and payable in like manner. If the whole or any portion of any assessment remains unpaid after the first 30-day period herein provided for, interest upon the whole unpaid sum shall be charged at the rate to be fixed by ordinance and each year thereafter one of the installments, together with interest due upon the whole of the unpaid balance, shall be collected. Any installment not paid prior to the expiration of the 30-day period during which such installment is due and payable shall thereupon become delinquent. All delinquent installments shall be subject to a charge for interest at the rate fixed in the ordinance levying the assessments and to an additional charge of 12 percent penalty levied upon both principal and interest due on such installment or installments. (Ord. 2232 § 1, 1999; Ord. 543 § 2, 1970; Ord. 84 § 10, 1961)