Okla. Stat. tit. 68, § 258

Notwithstanding the provisions of any statute to the contrary, employees of the Tax Commission may personally serve the necessary summons or notice issued for any hearing, civil proceeding, or criminal proceeding initiated by the Tax Commission pursuant to any state tax law. Service by the Tax Commission pursuant to this section shall have the same force and effect as if such service had been made by any other person authorized by law to perform such service. The provisions of this section shall not authorize the execution of tax warrants by the Tax Commission.