20 CFR § 404.1519h
Your medical source
February 18, 2021
When, in our judgment, your medical source is qualified, equipped, and willing to perform the additional examination or test(s) for the fee schedule payment, and generally furnishes complete and timely reports, your medical source will be the preferred source for the purchased examination or test(s).
[82 FR 5866, Jan. 18, 2017]