Okla. Stat. tit. 43, § 118.4

Assignment or transfer of child support benefits - Attorney fees. A. Child support or any claim thereto shall not be directly or indirectly assigned, except as provided in subsection B of this section and in subsection C of Section 237 of Title 56 of the Oklahoma Statutes. Any assignment of child support to the Department of Human Services shall have first priority over any prior or subsequent assignment. B. Child support may be assigned to an attorney for the purpose of providing legal representation in child support proceedings. The assignment shall be consistent with the Oklahoma Rules of Professional Conduct and shall not exceed fifty percent (50%) of the net amount of the child support collected and remitted to the obligee.