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).
What's new for 2026
- Statewide — the Safer Homes summary is now page 1. Since January 1, 2026, 765 ILCS 752 (P.A. 103-1031) requires the IDHR-published Summary of Rights for Safer Homes to be attached as the first page of every written residential lease, new or renewal, with the tenant acknowledging receipt. Omitting it costs at least $100 plus attorney fees. This is in addition to — not instead of — the RLTO or RTLO summary. BuildMyLease prepends the current IDHR form to every Illinois lease automatically.
- Chicago — the 2026 deposit-interest rate is 0.01% (§ 5-12-080; the Comptroller sets it annually), and the current-rate summary must be attached alongside the RLTO summary (§ 5-12-170).
- Chicago — Fair Notice tiers still govern renewals and increases. Under § 5-12-130, a landlord must give 30 days' written notice (tenancy under 6 months), 60 days (6 months to 3 years) or 120 days (over 3 years) before declining to renew, terminating, or raising the rent by any amount.
- Chicago — the late-fee cap, stated precisely: $10 per month on the first $500 of monthly rent plus 5% of the amount over $500 (§ 5-12-140) — $35 on a $1,000 rent.
- Suburban Cook County — the RTLO numbers: late fees capped at $10 per month on the first $1,000 of rent plus 5% of the excess; deposit capped at 1.5× a month's rent (the excess payable over six months) and returned within 30 days with an itemization; the County's RTLO summary attached to every lease and renewal, with a two-business-day cure if it was missed.
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 residential lease agreement 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.