California Code, Government Code - GOV § 16303

If money withdrawn from the Treasury pursuant to a valid act of appropriation is subsequently returned, in whole or part, the Controller shall credit it back to the special or general appropriation from which it was drawn, and it is available for the purpose for which it was appropriated.

Money so returned after expiration of the period of availability of such appropriation may be credited by the Controller to either the appropriation or the fund from which it was drawn. In making such determination, the Controller shall take into account, among other things: the amount of the abatement, the time elapsed since the reversion of the appropriation, and the undisbursed balance remaining in the appropriation.