Retired members of this system, and beneficiaries who are entitled to receive allowances or benefits under this part, may authorize deductions to be made from their retirement allowance payments or from the allowances and benefits, respectively, or from either or both when both are being received in accordance with regulations established by the board for the payment of charitable contributions under any plan approved by the board. In lieu of approving individual plans, the board, at its discretion, may adopt by reference those plans approved by the Department of General Services under Section 13923. The board shall determine the additional cost involved in making deductions under this section, and the agency to receive the contributions shall pay the amount of the

additional cost to the board for deposit in the retirement fund.