Up to this point, TIGHTPNO DLPNO-CCSD(T 0 ) has been used as a reference. However, the approximations that have already been introduced in this approach naturally lead to deviations from canonical CCSD(T) results. The question arises how pronounced the effect is and whether the error of the multi-level approach adds up or cancels out to the TIGHTPNO DLPNO-CCSD(T 0 )