The Commissioner may provide by regulation for the exclusion from taxable receipts, amusement charges of amounts representing sales where the contract of sale has been cancelled, the property returned on the receipt or charge has been ascertained to be uncollectible or, in the case the tax has been paid upon that receipt or charge, for refund or credit of the tax so paid. (Added 1969, No. 144, § 1, eff. June 1, 1969.)