Illinois Lease Agreement: Chicago RLTO, Cook County RTLO, Radon Disclosure (2026)

State-level statutes you cannot ignore

The Illinois Security Deposit Return Act, 765 ILCS 710, applies only to landlords of buildings with five or more units. For covered landlords, the Act requires return of the deposit, less itemised deductions, within 45 days after the tenant vacates, with paid receipts furnished within 30 days if any deduction is claimed. The Act does not cap the deposit amount. Failure to comply gives the tenant statutory damages of twice the deposit amount, plus costs and reasonable attorney fees, under section 1.

The Illinois Security Deposit Interest Act, 765 ILCS 715, applies to landlords of 25 or more units. Covered landlords must pay interest on deposits held more than 6 months, at the rate set annually by the state (tied to the average savings rate of insured Illinois commercial banks). Interest must be paid annually, by cash or credit against rent. Many smaller landlords confuse this requirement with Chicago RLTO interest (which has a separate, typically higher rate). The state rule applies only to 25-plus-unit landlords.

The Illinois Radon Awareness Act, 420 ILCS 46, requires landlords to disclose known radon hazards before the lease is signed and to provide the IEMA pamphlet titled "Radon Guide for Tenants." The requirement applies to all leases entered or renewed on or after 1 January 2012, statewide, in any unit at or below the third floor. The disclosure must be in writing. The pamphlet must be either delivered or made available; landlords often satisfy the requirement by including a link to the IEMA website along with the written disclosure. Failure to disclose can support a tenant's claim for damages and rescission.

The Illinois Lead Hazard Mitigation Act, 410 ILCS 45, layers state lead obligations on top of the federal lead-based paint rule. The state rule requires owners of certain pre-1978 properties to develop a mitigation plan if a child under 6 is in residence and a lead hazard is identified. For most rental landlords, the federal disclosure satisfies pre-tenancy obligations, but Illinois layers additional duties if lead is found.

Chicago RLTO: the heart of Illinois landlord-tenant law

The Chicago Residential Landlords and Tenants Ordinance, Chicago Municipal Code Chapter 5-12, applies to most rental units within Chicago city limits. The principal exclusions are owner-occupied buildings of six or fewer units (where the owner lives in one of the units), hotels and motels for transient stays, school dormitories, hospitals, and shelters. Effectively, most Chicago apartment landlords are RLTO-covered.

The RLTO imposes substantial obligations. Section 5-12-080 governs deposits: the landlord must place the deposit in a federally insured Illinois account separate from the landlord's funds, disclose the bank name and address in the lease or in a separate notice within 14 days, pay interest at the City Comptroller's rate on deposits held more than 6 months, and return the deposit within 45 days. The first violation (failure to disclose the bank) triggers statutory damages of the deposit amount; subsequent violations can trigger statutory damages of twice the deposit.

Section 5-12-170 requires the landlord to attach a written summary of the RLTO to every new lease and to every renewal. The summary is published by the City of Chicago Department of Housing and is updated periodically; landlords using the older 2017 summary in 2026 leases are technically non-compliant. The summary requirement is a frequent source of small-claims judgments because the statutory damages are 100 dollars per violation, automatic, and easy for tenants to prove.

Section 5-12-110 gives tenants a statutory repair-and-deduct remedy. After 14 days written notice of a habitability defect, the tenant may have the repair made and deduct the cost (capped at one-half month's rent or 500 dollars, whichever is greater) from the next rent payment. The remedy is broader than Illinois state law and is one of the most-litigated provisions of the RLTO. Tenant compliance with the strict notice procedure is essential; landlords who can show defective notice typically defeat the deduction claim.

Section 5-12-130 governs notice for non-renewal and rent increases. The landlord must give 30 days written notice for tenancies of less than 6 months, 60 days for tenancies of 6 months to 3 years, and 120 days for tenancies of more than 3 years. The notice rules cover both non-renewal and rent increases regardless of percentage. The 120-day rule for long-term tenants is more protective than the New York HSTPA sliding scale and frequently surprises Chicago landlords accustomed to month-to-month management.

Cook County RTLO and other local ordinances

The Cook County Residential Tenant and Landlord Ordinance, effective 1 June 2021, extends RLTO-like protections to most unincorporated Cook County rental units and to municipalities that have not opted out. Several municipalities (Evanston, Skokie, Mount Prospect, Oak Park, and others) opted out before the deadline, retaining their own local ordinances or defaulting to state law. The Cook County RTLO closely mirrors the Chicago RLTO on deposit handling, notice, repair-and-deduct, and disclosure. The principal differences are administrative: enforcement runs through Cook County rather than the City of Chicago, and the statutory summary is a different document.

Evanston's Residential Landlord and Tenant Ordinance (Evanston Municipal Code Chapter 5-3) predates the Cook County RTLO and remains in force after the Evanston opt-out. The Evanston ordinance has broadly similar deposit-handling rules but with shorter notice periods. Mount Prospect, Oak Park, and Urbana operate their own ordinances. Naperville's source-of-income protection extends to Section 8 vouchers under a Human Rights Ordinance amendment in 2022.

The take-away for an Illinois landlord drafting a 2026 lease: identify which ordinance applies before doing anything else. A lease compliant with Chicago RLTO is not automatically compliant with Cook County RTLO (and vice versa), and a lease compliant with neither may still be enforceable in downstate Illinois where no local ordinance applies. The state-law-only framework (765 ILCS 710 plus the radon disclosure plus the federal lead rule) suffices in Springfield, Peoria, and most counties south of I-80, but layers of local rules apply north of there.

Late fees, termination, and eviction

Illinois state law does not cap late fees beyond a general unreasonable-penalty doctrine. Chicago RLTO section 5-12-140(h) caps late fees at 10 dollars per month for rent under 500 dollars, and 5 percent for rent of 500 dollars or more, after a 5-day grace period. The Cook County RTLO uses the same formula. Landlords charging higher late fees in covered jurisdictions face statutory damages.

Termination of a month-to-month tenancy under 735 ILCS 5/9-207 requires 30 days written notice. For Chicago RLTO and Cook County RTLO units, the longer notice periods in the local ordinances apply (up to 120 days for long-term Chicago tenants). Eviction for non-payment requires a 5-day notice to pay or quit under 735 ILCS 5/9-209. Eviction for lease violations requires a 10-day notice under 735 ILCS 5/9-210. After the notice period expires, the landlord files a forcible entry and detainer action in circuit court. Cook County eviction timelines run typically 4 to 8 weeks; downstate timelines are usually faster.

For step-by-step eviction templates and the full state-by-state timeline, see the eviction notice page.

Sample Illinois-specific clauses

Security deposit clause (Chicago RLTO compliant)

Illinois radon disclosure (420 ILCS 46)

Notice of bank (Chicago RLTO)

How Illinois sits among the major states

Illinois is a study in regional contrast. Downstate Illinois (no local ordinance) sits closer to Indiana or Iowa: minimal state code, no deposit cap, no late-fee cap, fast eviction. Chicago and Cook County sit closer to New York or California in protective scope: deposit interest, repair-and-deduct, sliding-scale notice, statutory summary requirements. Same state, very different leases. See the California page for the highly regulated comparator, the Texas page for the permissive contrast, and the state hub for the full comparison table.

Frequently Asked Questions

Sources

• Illinois Security Deposit Return Act (765 ILCS 710): ilga.gov
• Illinois Security Deposit Interest Act (765 ILCS 715): ilga.gov
• Illinois Radon Awareness Act (420 ILCS 46): ilga.gov
• Chicago Residential Landlords and Tenants Ordinance (Chapter 5-12): chicago.gov
• Cook County Residential Tenant and Landlord Ordinance: cookcountyil.gov
• 735 ILCS 5/9-207 (notice for monthly tenancies) and 735 ILCS 5/9-209, 5/9-210 (eviction notices): ilga.gov
• EPA lead-based paint disclosure: epa.gov/lead