No change in the option selected shall be permitted after the member's death or after the member has received a retirement benefit except as provided in Section 104. This prohibition extends to a member's option to receive a refund of the amount of accumulated employee contributions and interest in lieu of receiving a retirement benefit. For purposes of this Regulation, "receipt of a retirement benefit" means negotiating or cashing a benefit payment. Except as specifically provided by law, a member may not change an option after 90 days from the date the first benefit payment is issued even if such payment is not negotiated or cashed.
27 Miss. Code. R. 210-35-103