Licence plates with a data medium and a slot antenna have low transmission and reception performance for electromagnetic waves as a rule. Moreover, the positioning of the slot antenna is severely limited by an inscription on the licence plate. The invention provides a licence plate with a data medium and an antenna with improved transmission power and at the same time sufficient space for the positioning of the antenna. This is achieved by a licence plate body of the licence plate having at least one cavity, and a front of the licence plate body or a coating of the front of the licence plate body covering the cavity comprises a slot structure forming the antenna.