All assessments of the additional levy shall be computed on the latest business license tax paid or payable on record as of August 15 of each calendar year, provided, that for the purpose of determining the additional levy for water utility franchise license taxes covered in Section 19-24 of this Code, the base business license will be computed on the same basis and at the same rates as specified for other business under Section 19-27 of this Code. All assessments of the one hundred percent additional levy will be due and payable in advance on September 1 of each year for the period commencing September 1 of each year and ending August 31 of the succeeding year, and will become delinquent if not paid by September 30 following the due date; provided, however, that assessments of the one hundred percent additional levy may be paid in equal installments on September 1 of the year due and payable and on March 1 of the succeeding year, and the installment due on the latter date will become delinquent if not paid by March 31. Delinquent licensees shall be subject to the same penalties for late payment as provided in Section 19-21 of this Code with respect to annual business licenses. (Ord. No. 1635 (NCS), § 4.)