which shows a high sensibility to the employed DLPNO thresholds and the triples cutoff. Additionally, the DLPNO-(T 0 ) approximation was already proven problematic before for reaction 64 of the pericyclic reactions from the BH9 set which is known in rare cases for small gap systems. This high sensibility in case of aug-cc-pVQZ is assumed to be related to a smaller HOMO-LUMO gap compared to other employed basis sets. This can be probably overcome by the iterative DLPNO-(T) algorithm by Guo et al. It has been shown in Sec. 3.3 that smooth potential energy surfaces can be calculated with a target accuracy of TIGHTPNO while NORMALPNO shows discontinuities. For the description of weakly interacting complexes, at least TIGHTPNO is required as the majority of pair correlation energies are relatively small and are thus likely to be excluded from the CCSD equations, as shown for stacking interactions in dimeric BODIPY dyes (Sec. 3.5). For the latter, it was demonstrated that the pair-selected multi-level approach can drastically reduce the number of triples. This could be taken advantage of for a computationally more efficient DLPNO-(T) correction within the pairselected multi-level approach. However, it also raises the question whether a different treatment of the triples may be required in the multi-level context in combination with the iterative DLPNO-(T)