Whenever a retiree, beneficiary, survivor, or other person illegally obtains money or benefits which are not due them, the repayment of such overpayment to the system or the recovery of the overpayment as authorized by R.S. 11:192 shall include interest to be paid to the retirement system at the rate of legal interest, and shall be computed from thirty days after the date the system requests repayment.
La. Consolidated Public Retirement § 11:894