40 ILCS 5/12-136.1
An employee may elect to take a lesser retirement annuity reduced by not more than 1/3 thereof and provide an optional reversionary annuity for a surviving spouse derived from the actuarial value of his retirement annuity; provided (a) a written notice of election by the employee to provide such annuity is received by the board at least 1 year before the date of his retirement, except that for an employee retiring prior to July 1, 1964, such notice must be given the board at least 60 days before his retirement, (b) the amount of the optional reversionary annuity as specified in the employee's notice of election is not less than $100 per month nor more than the employee's reduced retirement annuity, and (c) death of the employee occurs after retirement.
The employee may revoke the election if notice thereof is received by the board at least 1 year before the date the retirement annuity begins. The death of the employee or death of the spouse prior to retirement of the employee shall constitute an automatic revocation of the election.
No option shall be permitted in any case where the reversionary annuity for a wife, when added to the widow's annuity provided herein, exceeds the reduced retirement annuity payable to the employee.
The increases in the retirement annuity provided in Section 12-133.1 shall, as to a member so electing a reversionary annuity, be applicable to the amount of the reduced retirement annuity.
An optional reversionary annuity shall begin on the day next following the annuitant's death. If the beneficiary does not survive the annuitant, no such annuity shall be payable.
40 ILCS 5/12-136.1