Tennessee Code Title 56. Insurance § 56-2-123

If verbal authorization is given to a health care provider, insured, or enrollee for medical care under any individual, franchise, blanket or group health insurance policy, medical service plan or contract, hospital service corporation contract, hospital and medical service corporation contract, fraternal benefit society, health maintenance organization, or managed care organization, the verbal authorization shall be confirmed by written authorization, facsimile transmission, or verbally by means of a confirmation number or other confirmation code.