Here, our focus is on AM1-BCC charges as these are heavily used by the Open Force Field and Open Free Energy projects which form the basis for our own typical binding free energy calculations. Particularly, we compare several di erent approaches for assigning AM1-BCC charges -using AmberTools AM1-BCC charges, OpenEye AM1-BCC charges, and OpenEye AM1-BCC ELF10 charges. We show that partial charge assignment can dramatically impact free energy calculations (including binding free energies) due to apparently small variations in user input or even choice of computer architecture, meaning that significantly more e ort may need to be paid by method developers to provide conformer-independent charges.