We first look at the impact of the type of triples correction on the DLPNO-CCSD(T)/CBS (3,4) energies. The mean absolute deviation (MAD) of 1.255 kcal/mol for DLPNO-CCSD(T 0 )/CBS (3,4) when compared to DLPNO-CCSD(T 1 )/ CBS (3,4) is heavily influenced by Hc 1RE2, for which there is a difference of over 5 kcal/mol. This is likely due to the mild multireference character of the structures involved in this step-Semidalas and Martin have noted a link between sensitivity to the triples correction and static correlation. Across the other four reaction steps (CDO 1RE1 and 1RE2, NiSOD 1RE4 and Hc 1RE1), the MAD is only 0.290 kcal/mol. The majority of systems in the MME set, however, are large enough to necessitate an estimated level of theory for their reference values, and we do not wish to have the additional error of the (T 0 ) triples correction on top of the error associated with the estimation scheme. For example, the MAD of estimated CBS(3,4) using (T 1 ) triples is 0.234 kcal/mol as seen in table , but when the (T 0 ) triples energy is used instead, the MAD becomes 1.650 kcal/mol. Even excluding Hc 1RE2 from this small test set again, the error of the estimated CBS (3,4) approach is still more than twice as high when (T 0 ) triples are used instead of (T 1 ) (0.548 kcal/mol vs 0.244 kcal/mol). We therefore use the (T 1 ) triples procedure to calculate all reference values for the set.