The answer depends on the type of beneficiary you are nominating (person, trust or organization) and the type of death benefit you are nominating that beneficiary for.
Person – NYCERS does not require supporting documentation if the person is nominated for an Ordinary Death Benefit by an active or vested member, or a Five-/Ten-Year Certain Retirement Option by a retiring member.
When nominating a person for a Joint & Survivor Death Benefit (for your retirement option election), NYCERS requires a proof of birthdate, and, if the person has a history of name changes, a Marriage Certificate, Judgement of Divorce, or Court Order for each name change.
Trust – To nominate a Trust as a Beneficiary, you must submit the entire Trust document or the Last Will and Testament containing the Trust provisions.
Organization – Supporting documentation is not required.