40 ILCS 5/5-201
The following amounts shall be credited to this reserve: (1) amounts transferred from the city contribution reserve and from the salary deduction reserve for the payment of annuities which have been fixed; (2) amounts deducted from the salary of a policeman after the amount of his age and service annuity has been fixed; and (3) amounts transferred to this reserve from the investment and interest reserve.
All age and service annuities and all widow's annuities shall be charged to this reserve. Any amount to be refunded under this Article shall be charged to this reserve.
If a policeman whose annuity is fixed or granted withdraws from service and thereafter re-enters service before age 63, an amount determined in accordance with this Article shall be charged to this reserve and credited for age and service annuity in the city contribution reserve and the salary deduction reserve, respectively. Such amount shall be credited in such reserves in the ratio in which the respective amounts transferred from such reserves for age and service annuity for the policeman bear to each other at the time his annuity was fixed. If the wife of such policeman when he re-enters service was his wife when annuity for his wife was fixed an amount to be determined as provided in this Article shall be transferred from this reserve and credited to the policeman for widow's annuity in the city contribution reserve and the salary deduction reserve, respectively. Such amount shall be credited in such reserve in the ratio which the respective amounts transferred bear to each other at the time the annuity for the wife was fixed.
40 ILCS 5/5-201