Cash register system, comprising - a plurality of stationary units, which are respectively connected via at least one physical connection (4.1, 4.2, 4.3) to in each case at least one cash-register peripheral unit (5.1, 5.2, 5.3), - a mobile unit, comprising a display device, and an input device, wherein the mobile unit is set up to execute cash register software, in the process of which the cash-register peripheral unit (5.1, 5.2, 5.3) is accessed via a driver on the mobile unit for a virtual interface, - a management unit, which is different from the plurality of stationary units, and which manages the plurality of stationary units and their cash-register peripheral units, wherein - the mobile unit can be connected to one of the stationary units via a first physical connection, - the mobile unit can be connected to the management unit via a second physical connection, which is designed as a network connection, - the stationary unit can be connected to the management unit via a third physical connection, which is designed as a network connection, and - the management unit is set up to check, on the basis of a set of rules, which determines whether a connection of the mobile unit to the stationary unit and its cash-register peripheral unit is allowed, whether a first logical connection of the mobile unit to the stationary unit and a second logical connection of the mobile unit to the at least one cash-register peripheral unit can be established, wherein a connection is referred to as a logical connection if it can physically take place via a number of different protocols and network technologies but for the mobile unit appears as a connection via a local interface to a local interface protocol, and if the check is successful, access to the stationary unit via the logical connection of the mobile unit and access to the cash-register peripheral unit (5.1, 5.2, 5.3) via the logical connection of the mobile unit is permitted, and the management unit detects a corresponding allowed logical connection, and wherein, to create the logical connection, the mobile unit and the stationary unit are designed to send an enquiry to the management unit in order that the management unit checks on the basis of the set of rules whether a logical connection of the mobile unit to the stationary unit and its cash-register peripheral unit (5.1, 5.2, 5.3) is allowed and, if it is allowed, the management unit thus sends a corresponding message to the mobile unit and the stationary unit in order to allow access via the logical connection, and otherwise a logical connection is not established. - a plurality of stationary units, which are respectively connected via at least one physical connection (4.1, 4.2, 4.3) to in each case at least one cash-register peripheral unit (5.1, 5.2, 5.3), - a mobile unit, comprising a display device, and an input device, wherein the mobile unit is set up to execute cash register software, in the process of which the cash-register peripheral unit (5.1, 5.2, 5.3) is accessed via a driver on the mobile unit for a virtual interface, - a management unit, which is different from the plurality of stationary units, and which manages the plurality of stationary units and their cash-register peripheral units, - the mobile unit can be connected to one of the stationary units via a first physical connection, - the mobile unit can be connected to the management unit via a second physical connection, which is designed as a network connection, - the stationary unit can be connected to the management unit via a third physical connection, which is designed as a network connection, and - the management unit is set up to check, on the basis of a set of rules, which determines whether a connection of the mobile unit to the stationary unit and its cash-register peripheral unit is allowed, whether a first logical connection of the mobile unit to the stationary unit and a second logical connection of the mobile unit to the at least one cash-register peripheral unit can be established, wherein a connection is referred to as a logical connection if it can physically take place via a number of different protocols and network technologies but for the mobile unit appears as a connection via a local interface to a local interface protocol, and if the check is successful, access to the stationary unit via the logical connection of the mobile unit and access to the cash-register peripheral unit (5.1, 5.2, 5.3) via the logical connection of the mobile unit is permitted, and the management unit detects a corresponding allowed logical connection, and wherein, to create the logical connection, the mobile unit and the stationary unit are designed to send an enquiry to the management unit in order that the management unit checks on the basis of the set of rules whether a logical connection of the mobile unit to the stationary unit and its cash-register peripheral unit (5.1, 5.2, 5.3) is allowed and, if it is allowed, the management unit thus sends a corresponding message to the mobile unit and the stationary unit in order to allow access via the logical connection, and otherwise a logical connection is not established.