In this paper, a spoof surface plasmon polaritons based reconfigurable bandstop filter is designed and simulated at a resonant frequency of 0.216 THz. The proposed filter design comprises corrugated L-shaped resonators that are excited using a spoof transmission line. The designed filter is simulated using Co-EM simulation and it is evident from the simulation results that the designed filter can be tuned from 0.216 to 0.219 THz by employing a variable capacitor. Microwave frequency design studies are conducted to validate the designed methodology experimentally, and the BSF is fabricated on a 1.52 mm thick Rogers R4003C substrate using an SMV 1430 varactor diode. The measured results indicate that raising the reverse bias voltages across the varactor diode from 0.5 to 10 V, shifts the resonance tuned over a frequency range of 0.03 GHz with 0.22 GHz absolute bandwidth. The designed THz filter holds the potential to be employed as a compact filter in polymer industries for spectroscopic imaging.