This paper is an extension of Novel Flexible Chip-less Bow-Tie RFID tag in which we presented the design, testing and fabrication of the tag and compared the results with Octagonal Chipless RFID tag. The chipless RFID tag was designed by using simulation software CST microwave studio and fabricated by using laser etching technique on a flexible polymer substrate Polyethylene Terephthalate (PET). The tag operates at frequency ranging from 8 to 18 GHz uses the Frequency Selective Surface (FSS) approach. A series of experiments are performed to measure the Radar Cross Section (RCS) in an anechoic chamber. The tag design is composed of six concentric Bow-Tie shaped loop resonators with one unitary element. In this paper, we demonstrated the Singularity Expansion Method (SEM) based circuit modelling and the transient behaviour of the RFID tag is performed. The coupling coefficients and the induced currents over the surface of Bow tie shaped rings are evaluated. The maximum read range is evaluated and the Bow-Tie RFID tag is proved to be more accurate and efficient with the variation of distance up to 1.8m at 0dBm which is extendable to 2.14m for higher input power. This range is maximum to our knowledge for such a high-frequency range of 8-18GHz. The 4-bits Bow-Tie Chipless RFID tag design is compact and can be deployed commercially for general IoT applications.