205 ILCS 625/10
Upon the death of the last surviving trustee or holder of the account, the institution that maintains the account shall distribute the proceeds to the beneficiary or beneficiaries designated in the agreement controlling the account without further liability. No institution, however, shall be required to distribute the account proceeds until the institution receives (i) legal evidence of death of all trustees or holders of the account, (ii) identification from each beneficiary then living, or business records evidencing the lawful existence and parties authorized to collect on behalf of each beneficiary not a natural person, and (iii) written direction from each beneficiary to close the account and distribute the proceeds in a form acceptable to the institution. If the institution, in its discretion, is unable to identify one or more beneficiaries, or cannot determine the lawful existence of any beneficiary, or cannot determine a party authorized to collect on behalf of any beneficiary, or if conflicting claims to the account are made by the beneficiaries or other interested parties, then the institution may refuse to distribute the proceeds, without liability to any beneficiary or other party, until the institution receives a determination of ownership by a court of appropriate jurisdiction.
205 ILCS 625/10