Illinois has one statewide residential landlord-tenant statute — but if your rental sits in Chicago or in suburban Cook County, a local ordinance layers extra rules on top, and those rules change what your lease must say. Two ordinances matter: the City of Chicago Residential Landlord and Tenant Ordinance (RLTO, Municipal Code of Chicago, Ch. 5-12) and the Cook County Residential Tenant and Landlord Ordinance (RTLO). Using a generic Illinois lease in either jurisdiction leaves required language out — and several of those omissions carry statutory penalties.
Which ordinance applies to your rental
The first question is always where the unit is:
- City of Chicago → the RLTO.
- Unincorporated Cook County and most suburbs → the Cook County RTLO (effective June 1, 2021).
- Evanston and Chicago are carved out of the county RTLO — each has its own ordinance, and Chicago's RLTO governs inside the city.
- Everywhere else in Illinois → state law only (765 ILCS 705 et seq.).
The RLTO also has exemptions. The most common one: owner-occupied buildings of six units or fewer are excluded from most of the ordinance (§ 5-12-020). If you live in your three-flat and rent the other units, most RLTO obligations won't apply — but a lease that says so is still the right move.
What the Chicago RLTO adds to your lease
The RLTO summary attachment (§ 5-12-170)
Every written rental agreement subject to the RLTO must have the City's RLTO Summary attached, along with a separate summary of the current security-deposit interest rate. Omitting the attachment is one of the most common — and most penalized — landlord mistakes in Chicago.
Security deposits (§ 5-12-080)
If you hold a deposit, the RLTO requires you to:
- hold it in a separate, interest-bearing account in an Illinois bank — never commingled with your own funds;
- give the tenant a written receipt;
- pay interest annually at the rate the Chicago City Comptroller sets each year; and
- return it with an itemized statement within the statutory window after move-out.
Mishandling the deposit exposes the landlord to statutory damages under § 5-12-080. This is the single most litigated RLTO provision.
Late fees and disclosures
The RLTO caps late fees well below the state's looser "reasonableness" standard (§ 5-12-140). And before signing, the landlord must disclose the owner or authorized manager, plus any known code violations or pending code-enforcement matters affecting the unit (§ 5-12-100).
What the Cook County RTLO adds (suburban Cook County)
For rentals in suburban or unincorporated Cook County — outside Chicago and Evanston — the RTLO mirrors much of the RLTO's spirit with its own specifics:
- Security deposit capped at 1.5× one month's rent.
- 48 hours' written notice before the landlord enters.
- Tenant remedies and disclosure duties comparable to the RLTO.
If your rental is in a suburb, confirm whether that municipality has opted out — a handful have — but the default across suburban Cook County is RTLO coverage.
The statewide Illinois floor still applies
Whether or not a local ordinance reaches your unit, Illinois law sets the baseline:
- The mandatory FEMA flood-hazard disclosure (765 ILCS 705/25, effective 2025).
- Deposit-return windows for buildings of 5+ units (765 ILCS 710/1) and deposit interest for 25+ units (765 ILCS 715/1).
- The Cook County rekey rule — change or rekey the locks before each new tenancy (765 ILCS 705/15).
- The prohibition on EFT-only payment — tenants must always have a paper-check or cash alternative (765 ILCS 705/4).
Common mistakes in Cook County leases
- Using a generic Illinois template in Chicago and omitting the RLTO summary attachment.
- Commingling the deposit instead of holding it in a separate interest-bearing account.
- Charging flat market-style late fees that exceed the RLTO cap.
- Assuming the county RTLO applies inside Chicago (it doesn't) or that Chicago's RLTO applies in the suburbs (it doesn't).
How to get a Cook County–ready lease
A correctly-built Illinois lease asks where the property sits, then branches: in Chicago it attaches the RLTO summary and applies the deposit-interest and late-fee rules; in suburban Cook County it applies the RTLO deposit cap and 48-hour entry notice; and everywhere it prints the statewide flood disclosure and rekey language. That's what we ship at BuildMyLease — generated from your wizard answers, with the right city/county clauses appearing only when they actually apply.
Build a Cook County–ready Illinois lease — $29 one-time, generated in 5 minutes, with the RLTO/RTLO scope toggles and the statewide flood disclosure baked in.
Statutory references
- Municipal Code of Chicago, Ch. 5-12 — Residential Landlord and Tenant Ordinance (RLTO).
- RLTO § 5-12-020 — exclusions, including owner-occupied buildings of six units or fewer.
- RLTO § 5-12-080 — security deposits, interest, and statutory damages.
- RLTO § 5-12-100 — landlord disclosures.
- RLTO § 5-12-140 — late-fee limits.
- RLTO § 5-12-170 — RLTO summary and deposit-interest-rate attachment.
- Cook County Residential Tenant and Landlord Ordinance (RTLO) — effective June 1, 2021.
- 765 ILCS 705/25, 705/15, 705/4; 710/1; 715/1 — Illinois statewide provisions.