To test the shifted-STM approach beyond the CORE65 data set, we next consider C(1s) ionization of ethyl trifluoroacetate. This molecule has four carbon atoms whose K-shell ionization energies are distinguishable, and as such it has been historically important in understanding XPS chemical shifts. This molecule has also been used to benchmark various theoretical methods. Our own results for ethyl trifluoroacetate are listed in Table alongside GW results from the literature. The SRC1-r1 and HFX functionals are not considered due to their relatively large errors in shifted-STM calculations. Amongst the GW methods, the evGW 0 @PBE approach affords the smallest MAE with respect to experiment, 0.2 eV. The ∆SCF calculations using SCAN, SCAN0, and B3LYP are also quite accurate, but errors are larger for BH&HLYP (MAE = 0.8 eV). Note that the absolute CEBEs in our SCAN results are slightly different from those reported in Ref. 17 where a numerical orbital representation was used, but the differences do not concern us given the SCAN functional's well known sensitivity to the quality of the numerical integration grid. As applied to ethyl trifluoroacetate, the original STM approach exhibits errors of 1-2 eV for some of the functionals tested. However, shifted-STM values (using β parameters optimized for the CORE65 test set) exhibit errors that are smaller than those obtained using GW methods. The best shifted-STM results are obtained with the LRC-ωPBEh functional, with a maximum error of only 0.04 eV for the four C(1s) ionization energies. However, none of the functionals considered in Table exhibit any errors larger than 0.17 eV. The β parameters therefore appear to be transferrable, which is not altogether surprising given the element-specific nature of XPS.