Payment of road-user charge
6.—(1)  The road-user charge for a motor vehicle shall be paid using ––
(a)an ERP card with sufficient stored value inserted in the in-vehicle unit installed in the motor vehicle; or
(b)a credit card which has been registered in advance with a participating bank and approved by the bank and the Registrar for the payment of road-user charges for that motor vehicle (referred to in these Rules as a registered credit card).
(2)  The appropriate amount of road-user charge payable under rule 5 shall be —
(a)debited in its entirety against the stored value of an ERP card inserted in the in-vehicle unit of the motor vehicle; or
(b)where an ERP card is not inserted in the in-vehicle unit of the motor vehicle or the ERP card inserted has a stored value that is insufficient to pay for the road-user charge, charged in its entirety to a registered credit card for that motor vehicle, if any.