Where a supplier of goods or services, as a condition of accepting payment by credit or debit card, requires the customer to pay an amount to himself or another undertaking, and where the total price payable by that customer is unaffected irrespective of how payment is accepted, that amount shall constitute an integral part of the taxable amount for the supply of the goods or services, under Articles 73 to 80 of Directive 2006/112/EC.