The present invention relates to a cashless vending system that utilizes a tethered payment interface. The tethered payment interface is mountable on the external surface of a vending machine while the payment module portion of the system resides inside the vending machine. An advantage of this system is that when a bill validator slot opening in the vending machine is available the tethered payment interface can be secured to an adapter plate and mounted in the available slot. However, when a slot opening in the vending machine is not available, then the tethered payment interface can be located and secured on the external surface of the vending machine. In addition, the tethered payment interface is configured to be user accessible, provide an informational display, accept magnetic cards (i.e. credit cards, employee badges, hotel room keys, others), and accept RFID device data (i.e. FOBS, touch, RFID credit cards, others).