Cal. Gov. Code § 20712

An election by any member or any employer to make additional contributions in accordance with Section 20710 shall be effective only if it was filed with the board on or before June 30, 1983. Additional contributions may be made on and after July 1, 1983, in accordance with the terms of an election filed on or before June 30, 1983. A refund of accumulated additional contributions or an application of accumulated additional contributions as payment of any required contribution under Section 20711 shall terminate the privilege of making additional contributions if the refund or application occurs on or after July 1, 1983.