35 ILCS 200/8-55
Within the Department, an Office of Appraisals shall assist local government assessment officials, in counties of less than 3,000,000 inhabitants, with appraisal of commercial and industrial properties having an assessment, prior to equalization by the Department, of $350,000 or more.
The Office shall provide assistance to assessors and Supervisors of Assessments having a complaint or appeal relating to the property to be appraised pending before the Board of Review or the State Property Tax Appeal Board. Such assistance shall be provided upon request, pursuant to a written agreement between the Department and the assessing official making the request, specifying the project involved, the time frame for making the appraisal, the purpose of the appraisal and the responsibilities of the parties, including agreement by the local assessing official that the appraisal will be accepted and utilized in the pending complaint or appeal.
35 ILCS 200/8-55