If any nontaxable charges are combined with and not separately stated from taxable service charges on the customer bill or invoice of a service supplier, the combined charge is subject to tax unless the service supplier identifies, by reasonable and verifiable standards, the portions of the combined charge that are nontaxable and taxable through the service supplier’s books and records kept in the regular course of business, and in accordance with generally accepted accounting principles, and not created and maintained for tax purposes. The service supplier has the burden of proving the proper apportionment of taxable and nontaxable charges. If the service supplier offers a combination of taxable and nontaxable services, and the charges are separately stated, then for taxation purposes, the values assigned the taxable and nontaxable services shall be based on its books and records kept in the regular course of business and in accordance with generally accepted accounting principles, and not created and maintained for tax purposes. The service supplier has the burden of proving the proper valuation of the taxable and nontaxable services. (Ord. 608 § 1, 2009. 2002 Code § 7-7.5).