415 ILCS 5/55.15

(a) Any retailer who fails to make a return, or who makes a fraudulent return, or who willfully violates any rule or regulation of the Department of Revenue for the administration and enforcement of the fee imposed by Section 55.8, is guilty of a Class 4 felony. (b) Any retailer who knowingly violates subsections (a) (2), (a) (3), or (b) of Section 55.8 commits a petty offense punishable by a fine of $100.