If the amount payable by any user for any two-month period is not paid on or before the twenty-first day of the calendar month immediately succeeding the month during which the two-month period ends, the amount payable for that two-month period shall be increased by adding to the amount computed as hereinbefore mentioned, a sum in the amount established by the annual fee ordinance. (Ord. 2023-12, 4-25-2023)