(a) The Commissioner may, in consultation with interested persons and agencies, promulgate a model bookkeeping system for use in reservation businesses. Until such model bookkeeping system is promulgated, each business owner shall keep records in accordance with generally accepted accounting principles.

(b) Each reservation business owner shall file with the Area Director an annual report on or before April 15 in a form approved by the Commissioner. Reports shall be subject to a yearly audit. The reports shall contain the names and respective interests of all persons participating in the business.

(c) The business owner or an employee shall record all sales and purchases whether for cash or credit. If the business is on the Navajo Reservation the owner or an employee shall supply the customer with a copy of the sale transaction containing a description of the article purchased or sold, the date of the transaction, and the price. A cash register receipt complies with this paragraph for grocery or dry goods purchases for cash.

(d) The licensee shall keep a duplicate copy of any writing required by paragraph (c) of this section for a period of not less than three (3) years and shall provide the customer or the customer's representative one copy of those writings upon request.