Okla. Stat. tit. 47, § 1139.1

At the time required for payment of any fee imposed pursuant to the provisions of the Oklahoma Vehicle License and Registration Act, any vehicle which is the subject of a lease or lease-purchase agreement between the owner of such vehicle and any county of this state shall be exempt from the fees so imposed. Owners of vehicles claiming the exemption provided by this section shall present adequate proof that the vehicle for which exemption is sought is the subject of a lease or lease-purchase agreement with a county of this state at the time any fee imposed by such act would otherwise be due. Service Oklahoma shall have the authority to determine what constitutes adequate proof as required by this section.