In this paper Stepped Impedance Resonator (SIR) is effectively used for the design of UWB Chipless RFID tag (3.1–10.6GHz). The properties of SIRs like independent control over the resonant modes, capability of placing higher harmonics away from the fundamental mode and control over the electrical length are effectively utilised in the design of proposed tag. RFID tag consist of 10 SIR is designed and fabricated in such away that its higher harmonic modes are designed to be outside the UWB spectrum. Theoretical, numerical and experimental results are also discussed in this paper. Backscattered signal from the tag is measured up to distance of 50cm.