The present invention relates to a chipless RFID tag (T), comprising: —a dielectric substrate (1); and —electromagnetic resonators (3) excitable by an external electromagnetic field and respectively arranged on separate spatial locations of the dielectric substrate (1) forming a row, and configured to resonate at a common resonant frequency. The dielectric substrate (1) defines several predetermined encoding areas that include the separate spatial locations, so that data is encoded by the presence/absence of operative electromagnetic resonators (3) thereon. The present invention also relates to a system comprising the chipless RFID tag of the invention and a RFID reader (R) reading an encoded code by detecting the presence/absence of attenuation peaks on an electromagnetic wave providing the external electromagnetic field to the electromagnetic resonators (3). The present invention also relates to a method for encoding data on a chipless RFID tag defined according to the present invention.