What happens if a Illinois tenant does not pay the increased rent?
If the increase notice was valid (correct form, correct advance period, effective on or after the notice's effective date), the higher rent is the legal rent on that date. The tenant who pays only the old amount is short-paying and the landlord may serve a pay-or-quit notice (5 days for pay-or-quit under 735 ILCS 5/9-209, 10 days for violations under 5/9-210) for the deficiency. If the increase notice was defective, the old rent is still the legal rent and the tenant is current. The defectiveness of an increase is a defense to eviction.
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.