CA Fam Code Section 4334

(a)

If a court orders spousal support for a contingent period of time, the obligation of the supporting party terminates on the happening of the contingency. The court may, in the order, order the supported party to notify the supporting party, or the supporting party’s attorney of record, of the happening of the contingency.

(b)

If the supported party fails to notify the supporting party, or the attorney of record of the supporting party, of the happening of the contingency and continues to accept spousal support payments, the supported party shall refund payments received that accrued after the happening of the contingency, except that the overpayments shall first be applied to spousal support payments that are then in default.