Temperature-programmed desorption techniques reveal the existence of a formate, located at the Cu-Zn interface, in a commercial Cu/ZnO/Al2O3 catalyst. At low adsorption pressures and after reduction of the catalyst, it is the predominant species on the surface. However, under typical industrial conditions, with pressures as high as 100 bars and fairly pronounced oxidising conditions, copper formate prevails on the surface. Discrepancies in the literature are ascribed to the occurrence of the interfacial formate.