Proper proof of disability shall consist of: (1) a written certificate by at least 2 licensed and practicing physicians designated by the System, certifying that member is disabled and unable to perform assigned duties; (2) a written statement from the employer certifying that the member is disabled and not receiving a salary, and related information as to the cause and commencement of disability; and (3) a written statement from the member certifying that the member is not and has not been engaged in gainful employment.
Occupational disability benefits under this Section shall be payable only if (1) on the basis of a claim filed by the applicant with the Illinois Workers' Compensation Commission, it is determined by the Commission that the disability was incurred while in the performance and within the scope of assigned duties, under the terms of the Illinois Workers' Compensation or Occupational Diseases Act, whichever applies, and the claim is adjudicated as compensable by the Commission under either of the aforesaid Acts; or (2) on the basis of a claim filed by the applicant with an insurance carrier with which the employer of the applicant has a workers' compensation insurance policy, it is determined under the terms of the aforesaid policy that the disability was incurred while in the performance and within the scope of the member's assigned duties and the claim is approved as compensable.
Any amounts provided for a member or a member's dependents under the Illinois Workers' Compensation Act, the Illinois Occupational Diseases Act or a workers' compensation insurance policy provided by the employer shall be applied as an offset to any occupational benefit provided under this Section in such manner as may be prescribed by the board.
In addition to the above benefit, the member shall receive creditable service and credit for contributions that the member would have made in active employment during the period of disability, except as provided in Section 16-149.6. Creditable service and credit for contributions shall be calculated on the basis of the annual salary rate used in computing the benefit; however, such credit shall not be used in the determination of the period for which disability benefits are payable. A member who remains disabled after the termination of benefits due to age or the expiration of the maximum period for which benefits are payable shall be entitled to the retirement annuity provided under Section 16-133, notwithstanding that the member may not have the required minimum period of creditable service prescribed for such annuity.
40 ILCS 5/16-149.1