The Illinois Real Estate assessed Valuation Complaint is a process for property owners who disagree with their assessed value of their real estate by the county assessor. Through this process, property owners can challenge the amount they are being charged in property taxes. There are three types of Illinois Real Estate assessed Valuation Complaint: formal complaint, informal complaint, and administrative review. A formal complaint must be filed with the county assessor or the Board of Review. An informal complaint is filed directly with the Board of Review. An administrative review is submitted directly to the Illinois Department of Revenue. In all cases, the property owner must provide evidence and documentation to support their claim that the assessed value is incorrect.