In most cases, employers install a GPS tracker in the vehicles they own to monitor the employee. However, this practice is not considered lawful without an established privacy policy, a balancing test and an associated privacy impact assessment, and we usually find infringing practices in many cases, so we summarize below how a GPS can be used legally, thus avoiding a potential fine. Based on the relevant practice of the Hungarian data protection authority, we hereby summarize the most important current data protection knowledge.