Federal regulations restrict health care providers' financial relationships with patients who have Medicare. Medicare is intended to provide comprehensive coverage. Providers who "opt out" of billing Medicare by charging their patients directly for their services are forbidden from seeking reimbursement from Medicare. This seems like common sense (or common decency), but it behooves both patient and provider to put this mutual agreement in writing.
To that end, as part of the first visit with any Medicare patient - even if it's the ONLY visit - we explain all this face-to-face and ask the patient to sign a standard "opt-out" contract before being seen by one of our providers.