Transcriptionist working for a large group of surgeons

You are a transcriptionist working for a large group of surgeons.  Dr. Knowles has limited office hours and spends much of this time at the two hospitals in which he has surgical privileges.  He frequently complains that his billing is delayed because his dictations require connection and there is often a lag of 2 weeks between dictation and authentication of the final report.  Dr. Knowles has asked you to sign his dictated report for him after he makes the corrections.  He says that, since he’s already read and approved the final report, this is OK.

How would you address this with Dr. Knowles?