Okla. Admin. Code § 590:10-21-4
All Retirees and Beneficiaries of the System are required to participate in the Excess Benefit Plan if their Retirement Benefit from the System for a Plan Year is limited during the applicable Calendar Year by Code Section 415(b). The Board shall determine for each Plan Year which Retirees and Beneficiaries are required to participate in the Excess Benefit Plan. Participation in the Excess Benefit Plan shall commence each Plan Year once a Retiree or Beneficiary has an Excess Benefit in that Plan Year as determined by the Calendar Year Code Section 415 limits. Participation in the Excess Benefit Plan shall cease for any portion of a Plan Year in which the Retirement Benefit of a Retiree or Beneficiary is not limited by Code Section 415(b) or if all benefit obligations under the Excess Benefit Plan to the Retiree or Beneficiary have been satisfied.
Okla. Admin. Code § 590:10-21-4