(40 ILCS 5/15-153.1) (from Ch. 108 1/2, par. 15-153.1)
    Sec. 15-153.1. Disability benefits - Reduction. (a) If a participant receiving disability benefits under this Article earns compensation from any source for personal or professional services in excess of the amount of the disability benefit, the disability benefit shall be reduced by the excess of the earnings over the benefit.
    (b) If a participant receiving disability benefits under this Article receives disability income under an insurance contract financed wholly or partially by the employer, the disability benefit shall be reduced by the amount so received.
    (c) In determining the monthly benefits payable under this Article, a deduction shall be made equivalent to any benefits payable to any employee under any State or Federal Worker's Compensation or Occupational Diseases Acts for any period for which disability benefits are payable. However, no deduction shall be made in the case of payment for medical, surgical and hospital services and artificial members or appliances, fixed statutory payments for the loss of any bodily member, or the permanent and complete loss of use of 100% of any bodily member, payments for the loss of industrial vision or redemption awards payable prior to the date monthly disability benefits first become payable. If the benefits deductible under this paragraph are stated as a specified amount per week for a designated calendar period, then the monthly amounts shall, for purposes of this Section, be 4 1/3 times such weekly amount.
    For any calendar month during which the amount of benefits deductible when thus computed on the monthly basis exceeds the amount of the monthly benefit otherwise payable under this Article for that month, no monthly disability benefit shall be payable under this Article. For any calendar month in which the amount of benefits deductible when computed on a monthly basis is less than the monthly disability benefit payable for that month, such lesser amount shall be deducted from the monthly disability benefit payable for that month. Lump sum awards provided for the payment in advance of workers' compensation benefits which are definitely allocable to specific weeks in a calendar period shall be deducted on the same basis as if the award had been payable on a weekly basis.
    If such workers' compensation is not allocable to any specific calendar period, including redemption awards payable subsequent to the date monthly disability benefits first become payable, an equivalent monthly amount of such awards shall be computed for the purposes of this Section as 4 1/3 times the amount of the weekly workers' compensation benefit provided by the applicable statute for the participant and his or her dependents. The total workers' compensation awards shall be divided by such computed equivalent monthly amounts to determine the number of months and fractions of months during which monthly disability benefits shall be reduced.
(Source: P.A. 83-1440.)