A fully printable, passive and planar chipless RFID transponder is presented. The chipless tag encodes data into the spectral signature using a multiresonator. Both amplitude and phase components of the spectral signature are used for data encoding. The tag comprises of a microstrip multiresonating circuit with 35 spiral resonators and two cross-polarized transmitting and receiving circular UWB monopol antennas. The chipless tag has potentials for low cost item tagging such as banknotes and secured documents.