40 ILCS 5/4-116
A firefighter with less than 20 years of service who (1) resigns or is discharged, or has been involuntarily laid off for other than disciplinary reasons for more than 180 calendar days, and (2) has not received any disability pension payments, is entitled to a refund of his or her total contributions during such service. Any firefighter receiving a refund under this Section forfeits and relinquishes all accrued rights in the Fund, including accumulated creditable service. In the event of reemployment in the service, the firefighter shall, prior to commencing service repay to the fund, to the extent that the municipality has not made such contribution on his or her behalf, the amount of any refund which he or she received upon resigning or being discharged. Upon repayment of this refund, the firefighter shall receive credit for the previous years of service for which he or she had received the refund.
40 ILCS 5/4-116