The Zapper Hub is an application, containing a suite of functionality, that enables Zapper payments and value-added services at a merchant.

The software is installed on a piece of hardware, or on a virtual machine, and connects to point-of-sale infrastructure through a local area network. Through the network, the Zapper Hub receives pro-forma invoices from the point-of-sale and returns a representation of that invoice in the form of a Zapper Code; either as a string or an image of a QR code. The QR code can be displayed on screens or sent to a local printer for the merchant's consumers to scan and pay with the Zapper app. The Hub also allows the point-of-sale to poll for payment notifications, returning payments made against an invoice, so that open invoices can be reconciled.

This document contains the required contracts for the Invoicing and Payment Notification functionality provided by the Zapper Hub.