40 ILCS 5/21-108

Upon approval of the coverage agreement submitted by an absolute or retirement system coverage group, the State Agency, on behalf of the State of Illinois, shall modify the Federal-State Agreement to extend coverage to employees of the coverage group consistent with the provisions of Section 218 of the Social Security Act, this Article and the approved coverage agreement. Such modification shall specify: (1) the coverage group or employee classification to be covered; (2) any employee classification to be excluded, or to continue to be excluded in the case of a modification to extend coverage to additional employee classifications of a covered political subdivision; (3) the approximate number of employees to be covered by the modification; (4) the title of the reporting official designated by the political subdivision as responsible for social security reporting to the State Agency; (5) the effective date of coverage; and (6) the controlling date for purposes of retroactive coverage.