The commissioner is authorized to promulgate, by rule, a convenience fee to cover the costs of issuing or renewing licenses, registrations and permits. Any fee set by rule under the authority of this section may be assessed in addition to the fee or fees assessed for the costs of issuing or renewing licenses, registrations and permits by mail or in person. In no event shall the fee exceed the actual costs incurred in issuing or renewing a license, registration or permit.
T.C.A. § 56-1-213