Agree with Merry...there is nothing you can charge when an insurance company processing the claims requests patient records/treatment notes, etc. It is at the provider's expense. If if was the patient requesting records, or a third party such as in a lawsuit, that would be a different story. But when the patient's insurance company wants the records, you send them, free of charge.
As it would appear, he may be being audited, so he shouldn't delay in sending in what they request. Some of the providers I work for get occasional requests from Medicare for treatment notes, and they are sent in same day as the request arrives.