820 ILCS 405/234
Subject to the provisions of Sections 235 and 245 C, "wages" means every form of remuneration for personal services, including salaries, commissions, bonuses, and the reasonable money value of all remuneration in any medium other than cash. The reasonable money value of remuneration in any medium other than cash shall be estimated and determined in accordance with rules prescribed by the Director. Such rules shall be based upon the reasonable past experience of the workers and the employing units concerned therewith.
Where gratuities are customarily received by an individual in the course of his work from persons other than his employer, such gratuities shall, subject to the provisions of this paragraph, be treated as wages received from his employer. Each such employer shall notify each such individual of his duty to report currently the amount of such gratuities to such employer and the Director shall, by regulation, prescribe the manner of notification and of reporting. The amount of gratuities so reported shall constitute a conclusive determination of the amount received unless the employer, within the time prescribed by regulation, notifies the Director of his disagreement therewith. Gratuities not so reported to the employer in the manner prescribed by such regulations of the Director shall not be wages for any of the purposes of this Act.
820 ILCS 405/234