In a method and arrangement for protecting a device against operation with unauthorized consumables a code number range for a device is allocated to a customer number in the memory of a data bank remote from the device. The consumable is aggregated with a generated code number which has a predetermined relationship to a reference code number from a group of reference code numbers that are stored in the device and lie in the aforementioned reference code number range. The allocation is stored in the data bank as a dataset with a customer number, a code number and an identification number of the consumable. In a device remote from the data center, a recognition of the need to change the consumable is recognized, whereupon a message is displayed for entering the code number, the validity and authenticity of the consumable in the device is checked on the basis of the entered code number and the reference code number range. The currently stored reference code number is then made unavailable for further use. The input of the code number can ensue via a chip card.