Cal. Educ. Code § 24616

Any overpayment made to or on behalf of any member, former member, or beneficiary, including but not limited to contributions, interest, benefits of any kind, federal or state tax, or insurance premiums, shall be deducted from any subsequent benefit that may be payable under either the Defined Benefit Program, the Defined Benefit Supplement Program, or the Cash Balance Benefit Program, except as provided in Section 24616.5. These deductions shall be permitted concurrently with any suit for restitution, and recovery of overpayment by adjustment shall reduce by the amount of the recovery the extent of liability for restitution.