40 ILCS 5/20-127

It shall be the duty and responsibility of an employee having pension credit in any participating system to make available such information or any other required data relating thereto, to the participating systems in which he has pension credits, in order that the pension credit may be applied in the manner herein provided. A participating system shall be under no obligation or responsibility to initiate any inquiry or investigation for the purpose of establishing pension credit in the case of any employee, in the absence of a request from the employee, accompanied by sufficient facts bearing upon the credit.