40 ILCS 5/11-166
Whenever the total amount accumulated to the account of a deceased employee from employee contributions for annuity purposes have not been paid to him, and in the case of a married male employee to the employee and his widow, both together, in form of annuity before the death of the last of such persons, a refund shall be paid as follows:
An amount equal to the excess of such amounts, over the amount paid on any annuity or annuities, or refund, without interest upon either of such amounts, shall be refunded to a beneficiary theretofore designated by the employee in writing, signed by him before an officer authorized to administer oaths, and filed with the board before the employee's death.
If there is no designated beneficiary or the beneficiary does not survive the employee, the amount shall be refunded to the employee's children, in equal parts, with the children of a deceased child taking the share of their parent. If there is no designated beneficiary or children, the refund shall be paid to the administrator or executor of the employee's estate.
If an administrator or executor of the estate has not been appointed within 90 days from the date the refund became payable, the refund may be applied in the discretion of the board toward the payment of the employee's burial expenses. Any remaining balance shall be paid to the heirs of the employee according to the law of descent and distribution of this State but assuming for the purpose of such payment of refund and determination of heirs that the deceased male employee left no widow of him surviving in those cases where a widow eligible for widow's annuity as his widow survived him and subsequently dies; provided, that if any child or children of the employee are less than age 18, such part or all of any such amount necessary to pay annuities to them shall not be refunded as hereinbefore stated but shall be transferred to the child's annuity reserve and used therein for the payment of such annuities.
40 ILCS 5/11-166