40 ILCS 5/12-143
Any employee disabled as the result of any cause other than injury incurred in the performance of an act of duty, while in actual service or in salary status within a period of 30 days from date of disability, whose absence from service without salary extends for 8 days or more, shall be entitled to an ordinary disability benefit. No benefit shall be payable if the total period of disability is less than 8 days.
The benefit shall begin to accrue from the first day of such absence and shall be payable during the period of disability, subject to the following limitations: (1) the maximum cumulative period for which the benefit is payable during the entire period of the employee's service shall be 1/4 of the employee's total credited service (excluding periods for which ordinary disability benefits were paid) or 5 years, whichever is the lesser; (2) if the disability is incurred after age 65, the 5 year period may be reduced if such reduction can be justified on the basis of actuarial cost data approved by the board upon the recommendation of the actuary.
The amount of benefit shall be 45% of the rate of salary of the employee at the time ordinary disability benefits commence together with the credits specified in Section 12-155; provided that if an employee reenters service and renders more than 30 days of actual employment in pay status performing the duties of his regularly assigned position, and again becomes eligible for ordinary disability benefit, the rate of salary to be used in the computation of his latest benefit shall be the rate in effect on the date of commencement of the last period of absence on account of disability.
40 ILCS 5/12-143