With smaller basis sets, especially ζ = D, the error is driven by the molecules with smallmagnitude OR as expected. In particular, the molecules that have the wrong sign with this basis set (molecule 27 for DFT and 2 for CCSD) account for a large part of the error, e.g., 18% of the total ∆ TQ U with aug-cc-pVDZ and LG(OI) for B3LYP and 44% with CAM-B3LYP. Significant improvement is observed going from ζ = D to T, with ∆ TQ U values going from 0.2-0.3 to 0.04-0.08 for DFT, respectively. However, CBS(DT) extrapolations seem to offer little improvement and even slightly worsen the result in the case of LG. Comparing the convergence across methods, B3LYP shows the fastest convergence with ba-sis set size, but CAM-B3LYP is only slightly worse. Not surprisingly, CCSD shows a more marked basis set dependence than DFT. Nevertheless, ∆ TQ U values with aug-cc-pVQZ only vary between 0.02 for LG(OI) to 0.04 for MVG. ∆ TQ U is always largest with MVG at CCSD level compared to the other choices of gauge; in fact, the MVG error is twice as large as that of LG(OI) for basis sets with ζ = T and Q. The data in Figure also show a rather random distribution of the errors and no particular correlation with the OR magnitude. The ∆ TQ S values (black horizontal lines crossing the bars in the plots) tend to be negative, indicating an overall underestimation of the reference values. However, this is again mostly driven by the molecules with small OR magnitude, especially those with the wrong sign from the ζ = D calculations.