The invention relates to a method and system for the user-specific initialization of identification devices in the field, particularly on-board units in road toll systems, based on a central facility, whereby each identification device, when delivered, has a unique device identification to which, in the central facility, a unique user identification is assigned, and in the central facility, an initialization PIN is generated from the device identification and from the user identification and is transmitted to the identification device from which the identification device, based on its device identification, computes the user identification for the user-specific initialization.