IL HB1427

Prohibits landlords from using algorithmic devices that incorporate nonpublic competitor data (such as actual rent prices, occupancy rates, and lease dates from competing landlords) to set or adjust residential rent amounts

Defines "algorithmic device" as software using algorithms to calculate rent data and advise landlords on pricing, but excludes monthly trade association reports with aggregated anonymous data and tools used for affordable housing program compliance

Applies to all residential rental agreements executed after the effective date, covering both initial rent setting and rent changes upon lease renewal

Violations constitute an unlawful practice under the Consumer Fraud and Deceptive Business Practices Act, exposing landlords to enforcement actions and penalties under that law

Legislative intent cites concerns about anticompetitive conduct, price fixing, and collusion allegedly facilitated by algorithmic rent-setting tools that have been subject to lawsuits