The choice of JKFit basis to pair with the cc-pVnZ-F12 orbital basis sets in F12 calculations has some additional considerations; there are currently no JKFit sets specifically matched to this family of orbital basis sets and, as seen in Table , the construction of the orbital sets means they have significantly reduced BSIE compared to cc-pVnZ. One option would be to develop new JKFit sets specifically for use with F12 basis sets, but given that the s and p primitives in the orbital basis are taken from the cc-pV(n+1)Z conventional sets it is feasible that an acceptable level of density fitting error may be achievable using an existing auxiliary basis set. Here we consider only the effect of the fitting basis on the DF-HF energy and any effects of the complementary auxiliary basis set (CABS) singles correction on the energy, or the possible effect of the JKFit basis on the integrals arising in F12 theory, are neglected.