The invention pertains to a method and system for determining a location of an identification tag (100) in a monitored area. The method comprises using a plurality of beacons (200) to broadcast (2010) beacon messages comprising an identification element relating to the originating beacon; receiving (2020) at a first set of beacons a localisation message from an identification tag (100), the tag having received (1010) a beacon message, extracted (1020) the identification element from the received beacon message, and transmitted (1030) information related to the identification element as part of the localisation message; performing (3010) a first level of localisation of the tag on the basis of characteristics of the respective copies of the localisation message received at the first set of beacons; and performing (3020) a second level of localisation of the tag on the basis of the information related to the identification element.