40 ILCS 5/17-118
A disability pensioner may be required to submit to an examination periodically by a physician or physicians appointed by the Board. The purpose of the examination is to establish whether the disability still exists and to determine whether the person is still incapacitated for teaching service or service as an employee of the Board. The Board may require disability pensioners to submit evidence of the continued existence of the disability. The Board may also employ investigative services to determine whether such pensioners are employed elsewhere as teachers or to establish whether they are still disabled.
The Board shall cancel a disability pension upon evidence that a pensioner is no longer incapacitated for teaching or service as an employee of the Board. However, if a pensioner has attained age 55 and has 20 or more years of service, the pension shall not be cancelled unless he is re-employed as a teacher or as a pensioner-substitute. If a disability pensioner is re-employed as a teacher or pensioner-substitute, the pension shall be cancelled on the first day of re-employment. The pensioner shall reimburse the Fund for pension payments received after the date of re-employment (if any), plus 5% interest compounded annually beginning one year after the Fund's notification of the cancellation and indebtedness. Upon cancellation of a disability pension, unless such person re-enters service and becomes a contributor, a refund shall be payable of the excess, if any, of the refundable contributions paid by him over the amount paid in disability pension.
40 ILCS 5/17-118