We are not aware of any limitations on check cashing fees in Illinois law. We do recommend that you review your account agreements to see if the fee is disclosed; this will ensure that you do not run into problems with non-customers who refuse to pay the check cashing fee when the check was written by a customer. (We wrote about this in Illinois Banker and can provide a copy of the article.)
The Illinois Banking Act has language similar to that cited in the website you found. Section 5e of the Act states that “[n]otwithstanding the provisions of any other law in connection with extensions of credit” banks may charge any fees based on its “prudent business judgment and safe and sound operating standards,” “subject only to the provisions of [subsection 4(1)] of the Interest Act.” 205 ILCS 5/5e. And subsection 4(1) of the Interest Act states that a bank is authorized “to receive or contract to receive and collect interest and charges at any rate or rates agreed upon by the bank or branch and the borrower.” 815 ILCS 205/4(1).