IL HB1827

Requires owners of income-producing properties in Cook County (3,000,000+ inhabitants) to submit annual income and expense data to the county assessor by July 1, with the first year deadline of September 1

Allows smaller counties to adopt the same requirement by ordinance or resolution, with a March 31 annual deadline

Exempts properties valued at $500,000 or less, residential properties with 6 or fewer units, hospitals, nursing homes, certain stadiums, and owner-occupied properties (where owner uses 80% or more of rentable space)

Imposes penalties of 0.025% of market value (maximum $10,000 per property) for failure to submit required data within 60 days of receiving a noncompliance notice

Protects submitted income and expense data from public disclosure under FOIA, requiring the assessor to compile and anonymize data before using it for mass appraisal purposes; unauthorized disclosure is a Class B misdemeanor with fines up to $7,500