625 ILCS 5/13-106
Every operator of an official testing station or official portable emissions testing company shall file with the Department, in the manner prescribed by the Department, a schedule of all rates and charges made by him for performing the tests provided for in Section 13-101 and Section 13-109.1. Such rate or charge shall include an amount to reimburse the operator of the official testing station or official portable emissions testing company for the purchase from the Department of the certificate of safety required by this chapter, not to exceed that fee paid to the Department by the operator authorized by this chapter. Such rates and charges shall be just and reasonable and the Department upon its own initiative or upon complaint of any person or corporation may require the testing station operator to appear for a hearing and prove that the rates so filed are just and reasonable. A "just and reasonable" rate or charge, for the purposes of this Section, means a rate or charge which is the same, or nearly the same, as the prevailing rate or charge for the same or similar tests made in the community where the station is located. No operator may change this schedule of rates and charges until the proposed changes are filed with and approved by the Department. No license may be issued to any official testing station or official portable emissions testing company unless the applicant has filed with the Department a proposed schedule of rates and charges and unless such rates and charges have been approved by the Department. No operator of an official testing station or official portable emissions testing company shall charge more or less than the rates so filed with and approved by the Department.
625 ILCS 5/13-106