"A vendor ID that uniquely identifies the law firm, as specified by the client. Could be the law firm's tax id number or other value used by the client to uniquely identify the law firm. Values required in this field may vary from client to client, but within a client's e-billing implementation only one such unique ID is allowed per law firm. Some client AP systems maintain multiple vendor IDs for a law firm that could be, for example, location dependent. It is not intended that multiple lf_vendor_ids for the same law firm would be supported by this field as they would be impossible to program into the law firm's time and billing software. Clients must choose only one unique identifier per law firm to be used in this field. "