40 ILCS 5/15-113.4
"Service for unused sick leave": A participant who is an employee under this System or one of the other systems subject to Article 20 of this Code within 60 days immediately preceding the date on which his or her retirement annuity begins, is entitled to credit for service for that portion of unused sick leave earned in the course of employment with an employer and credited on the date of termination of employment by an employer for which payment is not received, in accordance with the following schedule: 30 through 90 full calendar days and 20 through 59 full work days of unused sick leave, 1/4 of a year of service; 91 through 180 full calendar days and 60 through 119 full work days, 1/2 of a year of service; 181 through 270 full calendar days and 120 through 179 full work days, 3/4 of a year of service; 271 through 360 full calendar days and 180 through 240 full work days, one year of service. Only uncompensated, unused sick leave earned in accordance with an employer's sick leave accrual policy generally applicable to employees or a class of employees shall be taken into account in calculating service credit under this Section. Any uncompensated, unused sick leave granted by an employer to facilitate the hiring, retirement, termination, or other special circumstances of an employee shall not be taken into account in calculating service credit under this Section. If a participant transfers from one employer to another, the unused sick leave credited by the previous employer shall be considered in determining service to be credited under this Section, even if the participant terminated service prior to the effective date of P.A. 86-272 (August 23, 1989); if necessary, the retirement annuity shall be recalculated to reflect such sick leave credit. Each employer shall certify to the board the number of days of unused sick leave accrued to the participant's credit on the date that the participant's status as an employee terminated. This period of unused sick leave shall not be considered in determining the date the retirement annuity begins.
40 ILCS 5/15-113.4