Okla. Admin. Code § 715:10-17-5
Post-retirement employment in the public schools, institutions, and agencies covered by TRS is allowed after the break in employment outlined in OAC 715:10-17-2 has been met. Employment subject to this section shall include any services performed by a retired member, as defined in this subchapter, except for payments received as an employee of the State Department of Education pursuant to 70 O.S. § 17-103(F) or as an independent contractor or consultant, pursuant to a lawful contract that complies with the requirements of 70 O.S. § 6-101.2(B) and which is approved by TRS within sixty (60) days of the contract's effective date. TRS will follow guidelines in 70 O.S. §6-101.2(B) and federal guidelines from the Department of Labor and the Internal Revenue Service in determining when a retired person qualifies as an independent contractor or consultant.
Okla. Admin. Code § 715:10-17-5