(a) Any person taxable under this article having both cash and credit sales may report the sales on either the cash or accrual basis of accounting. Each election of a basis of accounting shall be made on the first return filed and, once made, the election shall be irrevocable unless the commissioner grants written permission for a change. Permission for a change in the basis of accounting shall be granted only upon written application and under rules and regulations promulgated by the commissioner.

(b) Any person reporting on a cash basis of accounting shall include in each return all cash sales made during the period covered by the return and all collections made in any period on credit sales of prior periods and shall pay the tax on the sales at the time of filing the return.

(c) Any person reporting on the accrual basis of accounting shall be allowed a deduction for bad debts under rules and regulations of the commissioner on the same basis that bad debts are allowed as a deduction on state income tax returns. In the case of an assignee of credit card debt purchased directly from a dealer without recourse, the assignee reporting on the accrual basis of accounting or a credit card bank which extends such credit to customers under a private label credit card program shall be allowed a deduction for bad credit card debts under rules and regulations of the commissioner on the same basis that bad credit card debts are allowed as a deduction on state income tax returns.