40 ILCS 5/7-139.2
An active member of the General Assembly having no service credits or creditable service in the Fund, may establish service credit and creditable service for periods during which he was an employee of a municipality in an elective office and could have elected to participate in the Fund but did not so elect. Service credits and creditable service may be established by payment to the Fund of an amount equal to the contributions he would have made if he had elected to participate plus interest to the date of payment, together with the applicable municipality credits including interest, but the total period of such creditable service that may be validated shall not exceed 8 years. Payments made to establish such service credit must be received by the Board while the member is an active participant in the General Assembly Retirement System, except that one payment will be permitted after the member terminates such service.
40 ILCS 5/7-139.2