The Compact Linear Collider (CLIC) is an e$^+$e$^-$ collider proposed as the next energy frontier machine at CERN. At the first running stage, at $\sqrt{s}=380$ GeV, it will allow for precise measurements of the Higgs boson and top quark properties, while the subsequent energy stages, at 1.5 TeV and 3 TeV, will mainly focus on searches for Beyond the Standard Model (BSM) phenomena.

The Inert Doublet Model (IDM) is a simple extension of the Standard Model, introducing an additional Higgs doublet that brings in four new scalar particles. The lightest of the IDM scalars is stable and is a good candidate for a dark matter (DM) particle. The potential of discovering the IDM scalars in the experiment at CLIC has been tested for two high-energy running stages, at 1.5 TeV and 3 TeV centre-of-mass energy. The CLIC sensitivity to pair-production of the charged IDM scalars was studied using the full detector simulation for selected high-mass IDM benchmark scenarios and the semi-leptonic final state. To extrapolate the results to a wider range of IDM benchmark scenarios, the CLIC detector model in Delphes was modified to take into account the $\gamma \gamma \to$ had. beam-induced background. Results of the study indicate that heavy charged IDM scalars can be discovered at CLIC for most of the considered benchmark scenarios, up to masses of the order of 1 TeV. Results included in this paper supersede results presented previously in DIS2021 proceedings.