You can file an appeal with the assessor on-line by going to http://www.cookcountyassessor.com or you can mail your complaint to the Assessor at 118 N. Clark, Chicago, IL 60602. Board of Review complaint forms can be downloaded from their web site at http://www.cookcountyboardofreview.com. Complaints cannot be filed electronically and must be delivered by hand to any of their five suburban satellite offices or mailed to their downtown office in the same building as the Assessor.