225 ILCS 320/37

Each governmental unit which is authorized to adopt and has adopted any ordinance or resolution regulating plumbing may provide for its administration and enforcement by requiring permits for any plumbing system installation, the inspection of plumbing system installations by inspectors who are licensed as plumbers in accordance with the Illinois Plumbing License Law, and the issue of certificates of approval or compliance which shall be evidence that a plumbing system has been installed in compliance with the Code of standards so adopted. A letter of intent shall be included with all plumbing permit applications. The letter shall be written on the licensed plumber of record's business stationery and shall include the license holder's signature and, if the license holder is incorporated, the license holder's corporate seal. If the license holder is not incorporated, the letter must be notarized. A governmental unit authorized to adopt regulations may, by ordinance or resolution, prescribe reasonable fees for the issue of permits for installation work, the issue of certificates of compliance or approval, and for the inspection of plumbing installations.