35 ILCS 105/7
It is unlawful for any retailer to advertise or hold out or state to the public or to any purchaser, consumer or user, directly or indirectly, that the tax or any part thereof imposed by Section 3 hereof will be assumed or absorbed by the retailer or that it will not be added to the selling price of the property sold, or if added that it or any part thereof will be refunded other than when the retailer refunds the selling price and tax because of the merchandise's being returned to the retailer or other than when the retailer credits or refunds the tax to the purchaser to support a claim filed with the Department under the Retailers' Occupation Tax Act or under this Act. Any person violating any of the provisions of this Section within this State shall be guilty of a Class A misdemeanor.
35 ILCS 105/7