  In this talk an investigation into the interference effects between the
process $pp\to \bar{t}bH^+$ followed by the decay $H^+ \to t\bar{b}$ and the
background process $pp \to t\bar{t}b\bar{b}$ is presented. The level of
interference in parts of the parameter space is shown to be high and as such it
may spoil the results of typical analyses which treat signal and background as
independent. This is shown for two benchmarks of the MSSM.
