Cal. PROB § 5136

(a) “Party” means a person who, by the terms of the account, has a present right, subject to request, to payment from a multiple-party account other than as an agent. (b) A P.O.D. payee is a party, by reason of being a P.O.D. payee, only after the account becomes payable to the payee by reason of surviving all persons named as original payees. (c) A beneficiary of a Totten trust account is a party, by reason of being a beneficiary, only after the account becomes payable to the beneficiary by reason of surviving all persons named as trustees.