When the business tax imposed by this chapter cannot be enforced without there being an apportionment according to the amount of business done in the city of San Luis Obispo, apportionment rules shall be established by the finance director. The finance director shall conduct an investigation and shall fix as the business tax for the applicant an amount that is reasonable and nondiscriminatory or, if a business tax has already been paid, shall order a refund of the amount over and above the business tax so affixed. In fixing the business tax to be charged, the finance director shall have the power to base the business tax upon a percentage of gross receipts, operating expenses, floor space, payroll, number of employees, business taxes paid to other cities, or any other measure which will assure that the business tax assessed shall be uniform with the amount of business done in the city of San Luis Obispo, or of businesses of a like nature, so long as the amount assessed does not exceed the business tax set forth in this chapter. (Ord. 1202 § 2, 1991)