40 ILCS 5/13-803
To make the payments authorized by this Article, the Board may keep and hold uninvested a sum not in excess of the amount required to make all annuity and disability benefit payments which shall become due and payable within the following 60 days. Such sum or any part thereof shall be kept on deposit in any bank or savings and loan association authorized to do business under the laws of this State. The amount deposited in any such bank or savings and loan association shall not exceed 25% of its paid-up capital and surplus.
No bank or savings and loan association shall receive investment funds as permitted by this Section, unless it has complied with the requirements, other than the maximum deposit requirement, established pursuant to Section 6 of "An Act relating to certain investments of public funds by public agencies", approved July 28, 1943, as now or hereafter amended.
40 ILCS 5/13-803