Errors associated with carboxylates and phenolates are lower than those of other groups, with RMSEs near 2 kcal mol -1 , close to the aleatoric limit of the QM calculations. At the other extreme, RMSEs for oxime anions exceed 8 kcal mol -1 (see Supporting Information (SI)). We advise potential users of this model to be wary of such potential stratification of performance based on functional groups. Our expectation is that errors from predicting gas-phase acidities of carboxylic acids and phenols will be significantly lower than those of other functional groups.