Cal. Unemp. Ins. Code § 1536

Any amounts determined by the director or his authorized representatives to be payable to employing units as refunds of contributions erroneously paid which are unclaimed at the end of three years from such determination shall be included in the revenue to the Unemployment Fund or in the case of interest or penalties, to the Contingent Fund. The employing unit or person entitled to such payment shall not thereafter maintain any claim, action or proceeding with respect to such amounts.