40 ILCS 5/9-179.1
A contributing employee may apply for creditable service for up to 2 years of military service whether or not the military service followed service as a county employee. The military service need not have been served in wartime, but the employee must not have been dishonorably discharged. To establish this creditable service the applicant must pay to the Fund, while in the service of the county, an amount determined by the Fund to represent the employee contributions for the creditable service established, based on the employee's rate of compensation on his or her last day as a contributor before the military service, or on his or her first day as a contributor after the military service, whichever is greater, plus interest at the effective rate from the date of discharge to the date of payment. If a person who has established any credit under this Section applies for or receives any early retirement incentive under Section 9-134.2, the credit under this Section shall be forfeited and the amount paid to the Fund under this Section shall be refunded.
40 ILCS 5/9-179.1