We report on a detailed Monte Carlo comparison of selection variables used to separate $tbH^\pm$ signal events from the Standard Model $t\bar t$ background. While kinematic differences exist between the two processes; whenever $m_{H^\pm} \ne m_W$, in the particularly challenging case of the near degeneracy of the charged Higgs boson mass with the $W$ mass, the exploration of the spin difference between the charged Higgs and the $W$ gauge boson becomes crucial. The latest implementation of the charged Higgs boson process into PYTHIA is used to generate the signal events. The TAUOLA package is used to decay the tau lepton emerging from the charged Higgs boson decay. The spin information is then transferred to the final; state particles. A fast and simple simulation of the expected detector response is applied. In case the $H^\pm$ mass is almost degenerate with the $W$ mass the; distributions of selection variables are very similar for signal and background. With the chosen selection variables the Iterative Discriminant Analysis (IDA) method; separates well signal and background, even in this scenario.