Why not simply use email?  Orders arrive and are dated.  You can verify back with the client.  Orders go out to your contractor, etc...

We actually include our complete chain of email correspondance in as part and parcel to each and every report that we do so that there is no room for ambiguity about what was requested, offered, or said.   Open, honest, up-front operations with our clients have never failed to serve us and them well.