The plots in Figures show that the TQ extrapolation is essentially at the CBS limit for DFT, with both functionals showing gauge invariance. For CCSD, the convergence towards the CBS limit is slower than for DFT, and it is due to the larger dependence of this level of theory on the basis set size compared to DFT. The CCSD ∆ TQ U values in Figure , up to 0.04, are slightly larger than for DFT, but they are small enough to consider the OR values essentially converged with respect to basis set size. All methods provide an almost perfect consistency in the OR sign with all basis sets, choices of gauge, and molecules. The only exceptions are molecules 27 for DFT and 2 for CCSD, which have a small OR magnitude and the calculations with the smallest basis set give the wrong sign with all choices of gauge. These two molecules are the main cause of the large relative errors with the aug-cc-pVDZ basis set in Figure . The CBS(DT) extrapolation offers little to no improvement over a regular aug-cc-pVTZ calculation for DFT, likely because the double ζ results are of poor quality. On the other hand, the CBS(DT) extrapolation provides significant improvement over the triple ζ results for CCSD-MVG, because this choice of gauge has a slower rate of convergence with basis set size. The slower convergence rate for MVG compared to LG and LG(OI) is consistent across methods (although the differences between gauges are small for DFT). In all cases, the results with the CBS(DT) extrapolation are farther from the CBS limit than those obtained with the aug-cc-pVQZ basis set, compare DT and Q sectors in the plots in Figure . Nev-ertheless, the aug-cc-pVQZ basis set is often prohibitive for production level calculations; therefore, using aug-cc-pVTZ for DFT calculations and the same basis with a CBS(DT) extrapolation for CCSD may provide the best cost/accuracy balance for OR calculations.