All fees and charges imposed under the provisions of this chapter are due and payable upon receipt of the notice of charges. Unpaid charges shall become delinquent twenty days after mailing or delivering the notice of charges. A basic penalty charge of twenty percent of the unpaid amount shall be added to any fee or charge that becomes delinquent. Interest at the rate of one-half percent per month shall accrue on the total of all delinquent charges plus all penalty charges. (Ord. 142 § 211, 1976)