Where the amount of the license fee or tax is based upon gross income, the taxpayer may pay his fee or tax in equal monthly installments during the life of his license, each such installment to be paid on or before the tenth day of the month. In all other cases the taxpayer may pay his fee or tax in equal installments during the life of his license, each such installment to be paid on or before the first day of February, the first day of May, the first day of August, and the first day of November, respectively. (Ord. 129 § 9, 1970).