IL HB4974

Caps annual property tax assessment increases at 15% over the previous year's assessed value and 40% over any 3-year period for commercial and residential properties in Cook County (counties with 3,000,000+ inhabitants), with other counties able to opt in by ordinance

Exempts from the assessment cap: new additions/improvements, property transfers, reclassified properties, expired incentive classifications, properties previously granted vacancy reductions, and technical error corrections

Requires the Department of Revenue to conduct a study on fairness and equity in property tax assessment processes, with preliminary report due May 31, 2023 and final report due July 1, 2023

Study must review Cook County's classification system compared to the rest of the state, including projections of phasing out the classification system and its impact on economic development and job creation

Mandates a 60-day public comment period in Cook County whenever the chief county assessment officer makes substantive changes to assessment procedures