Illinois has no statute equivalent to the California Mills Act. Instead, Illinois Property Tax Code 35 ILCS 200/15-40 and Cook County Class L assessment incentive provide property tax reductions for landmarked rehabilitation projects, freezing valuations rather than reducing rates.
California Mills Act contracts cap property taxes by formula for 10-year renewable terms. Illinois uses two parallel mechanisms. Statewide, 35 ILCS 200/15-40 Property Tax Assessment Freeze applies to owner-occupied historic residences listed on National Register or in certified districts, freezing assessed value for eight years then phasing back over four years. Cook County Class L extends a similar 12-year freeze on commercial or income-producing landmarks where rehab exceeds 50 percent of base value. Both require Illinois Historic Preservation Division certification of work meeting Secretary of Interior Standards. No formula-based ongoing valuation cap exists.
Falsifying rehab cost reports or failing to maintain qualifying status triggers retroactive recapture of the tax benefit. Owners owe back taxes plus interest. Class L recipients must complete approved scope before benefit activates.
See how Oak Park's mills act contracts rules stack up against other locations.
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