40 ILCS 5/6-195
All amounts which the city contributes for age and service annuity, widow's and supplemental annuity, except those contributed in lieu of deductions from salary of any fireman who receives duty disability benefit, and all amounts transferred to this reserve from the investment and interest reserve shall be credited to this reserve.
An individual account shall be kept in this reserve for each employee and for each widow for which the city shall contribute for supplemental annuity to which city contributions and interest shall be credited.
At least once each year, and always before any transfer is made from this reserve to any other reserve, the credits shall be improved by interest.
When the annuity for a fireman or widow is fixed, and when supplemental annuity for a widow first becomes payable, the total amount in this reserve for the purpose of providing such annuity and required therefor shall be charged to this reserve and credited to the annuity payment reserve.
If there is to the credit of any fireman who withdraws from service before age 63, an amount in excess of that required to provide him age and service annuity, or in excess of that required to provide widow's annuity for his wife (either or both) such amount shall be retained in this reserve and improved by interest until the fireman becomes age 63 or dies, whichever event occurs first. Any such accumulated amount shall then be used in accordance with the provisions of this Article.
40 ILCS 5/6-195