820 ILCS 405/1509
The Director shall promptly notify each employer of his rate of contribution for each calendar year by mailing notice thereof to his last known address. Such rate determination shall be final and conclusive upon the employer for all purposes and in all proceedings whatsoever unless within 15 days after mailing of notice thereof, the employer files with the Director an application for review of such rate determination, setting forth his reasons in support thereof. Such application for review shall be in the form and manner prescribed by regulation of the Director. If the Director shall deem any application for review insufficient, he shall rule such insufficient application stricken and shall serve notice of such ruling and the basis therefor upon the employer. Such ruling shall be final and conclusive upon the employer unless he shall file a sufficient application for review within ten days from the date of service of notice of such ruling. Upon receipt of a sufficient application for review within the time allowed, the Director shall order such application for review allowed in whole or in part, or shall order that such application for review be denied, and shall serve notice upon the employer of such order. Such order of the Director shall be final and conclusive at the expiration of ten days from the date of service of such notice unless the employer shall have filed with the Director a written protest and a petition for hearing, specifying his objections thereto. Upon receipt of such petition within the ten days allowed, the Director shall fix the time and place for a hearing and shall notify the employer thereof. At any hearing held as herein provided, the order of the Director shall be prima facie correct and the burden shall be upon the protesting employer to prove that it is incorrect. All of the provisions of this Act, applicable to hearings conducted pursuant to Section 2200 and not inconsistent with the provisions of this Section, shall be applicable to hearings conducted pursuant to this Section. In any such proceeding, the employer shall be barred from questioning the amount of the benefit wages or benefit charges as shown on any statement of benefit wages or statement of benefit charges which forms the basis for the computation of such rate unless such employer shall prove that he was not, as provided in Section 1508, furnished with such statement containing the benefit wages or benefit charges which he maintains are erroneous. In such event, the employer shall have the same rights to revision of such statement in such proceedings as are provided in Section 1508. Upon the completion of such hearing, the employer shall be promptly notified by the Director, by mail, of his decision, and such decision shall be final and conclusive for all purposes and in all proceedings whatsoever unless review is had within the time and in the manner provided by Section 2205.
820 ILCS 405/1509