PROB §5303: (a) The provisions of Section 5302 as to rights of survivorship are determined by the form of the account at the death of a party.

(a) The provisions of Section 5302 as to rights of survivorship are determined by the form of the account at the death of a party. (b) Once established, the terms of a multiple-party account can be changed only by any of the following methods: (1) Closing the account and reopening it under different terms. (2) Presenting to the financial institution a modification agreement that is signed by all parties with a present right of withdrawal. If the financial institution has a form for this purpose, it may require use of the form. (3) If the provisions of the terms of the account or deposit agreement provide a method of modification of the terms of the account, complying with those provisions. (4) As provided in subdivision (c) of Section 5405. (c) During the lifetime of a party, the terms of the account may be changed as provided in subdivision (b) to eliminate or to add rights of survivorship. Withdrawal of funds from the account by a party also eliminates rights of survivorship with respect to the funds withdrawn to the extent of the withdrawing party’s net contribution to the account.