How is a Illinois rent increase calculated when there is a percentage cap?
Take the current monthly rent, multiply by the cap percentage, and that is the maximum dollar increase. For example, a 5 percent cap on $2,000 monthly rent gives a maximum increase of $100, for a new rent of $2,100. Where the cap is "5 percent plus CPI capped at 10 percent" (such as California's AB 1482), look up the relevant regional CPI for the prior 12 months on the Bureau of Labor Statistics website. If CPI is 3 percent: 5 plus 3 equals 8 percent allowed (under the 10 percent cap). If CPI is 6 percent: 5 plus 6 equals 11 percent which is capped at 10 percent. If CPI is negative: only the base 5 percent applies. Round to the nearest dollar. Illinois has no statewide advance notice specific to rent increases. 735 ILCS 5/9-207 sets 30 days as the month-to-month termination default, which landlords treat as the minimum for rent changes. No state rent cap; local rent control is preempted statewide. Use a calculator rather than rely on memory; small CPI errors compound over multi-year tenancies.
Source: Lease-based; 735 ILCS 5/9-207 (30-day month-to-month termination default)
This is an informational answer based on Lease-based; 735 ILCS 5/9-207 (30-day month-to-month termination default) as of early 2026. It is not legal advice. Housing law changes year to year and local ordinances (especially in rent-controlled or rent-stabilized cities) can override or add to state law. For contested cases, consult a Illinois-licensed attorney.