in particular that all external particles are on their mass shell, that their residues are equal to one, and that the mixing contributions with all other particles vanish on-shell at the considered order. This requirement holds independently from the specific renormalisation scheme that has been adopted for a certain calculation. In case the renormalisation conditions of the chosen scheme do not impose the proper normalisation of external particles, the correct on-shell properties need to be established via UV-finite wave function normalisation factors (“Z-factors”). In the case of unstable particles, finite-width effects have to be taken into account, and more generally imaginary parts arising from the absorptive parts of loop integrals need to be properly treated. A further complication arises if ${\mathcal{CP}}$-violating effects are taken into account, since in this case the presence of complex parameters yields an additional source of imaginary parts. In the SM the different sources of imaginary parts affect for instance the renormalisation of the CKM matrix from the two-loop level onwards, see e.g. the discussion in Ref. [@Espriu:2002xv] and references therein. In the MSSM with complex parameters the corresponding effects arising from absorptive parts of loop integrals and complex model parameters enter predictions for physical observables 