Cook County Security Deposit Rules: What the Residential Tenant and Landlord Ordinance (RTLO) Adds to Illinois Law

A landlord in Cook County has to satisfy two sets of rules at once: the Illinois statute, 765 ILCS 710/1 (Security Deposit Return Act), and the county's own Residential Tenant and Landlord Ordinance (RTLO) (Cook County Code § 42-111). The state law sets the 45-day return deadline after termination of the tenancy; the local ordinance adds rules on deposit cap, paying the deposit in installments, return deadline and receipt and itemization. Where the two overlap, the landlord has to meet the stricter one.

What the Residential Tenant and Landlord Ordinance (RTLO) adds

• Deposit cap: Security deposits are capped at one and one-half months' rent regardless of what the charge is called. (42-111(a))
• Paying the deposit in installments: Any deposit portion above one month's rent may, at the tenant's election, be paid in up to six equal monthly installments. (42-111(b))
• Return deadline: Deposit must be returned within 30 days after the tenant vacates, with an itemized damage statement and paid receipts within 30 days if deductions are taken. (42-111(c))
• Receipt and itemization: Landlord must give a signed receipt stating amount, recipient, date and unit; failure entitles the tenant to immediate return of the deposit. (42-111(h)-(i))
• Other local rule: Deposits must be held in a federally insured Illinois account, not commingled, with the institution named in the lease; violations of (a)-(c) carry damages of two times the deposit plus attorney's fees. (42-111(d), (f), (m))

Who it covers: Dwelling units in suburban Cook County. Municipalities with their own landlord-tenant ordinance (Chicago, Evanston, Oak Park, Mount Prospect) are excluded, as are owner-occupied buildings of six or fewer units, a single owner-managed single-family home or condo that meets four conditions, hotel and rooming-house stays under 32 days, institutional housing, co-ops and employee housing (42-102).
Worth knowing: The county ordinance does not add an interest requirement; the Illinois Security Deposit Interest Act still applies where it does. Breaking the cap, installment or return rules costs the landlord two times the deposit plus attorney's fees.

What Illinois law already requires

• Return deadline: 45 days after termination of the tenancy.
• Detail: For landlords with five or more units: an itemized statement within 30 days and the refund within 45 days. Chicago's RLTO has its own 45-day rule and double-deposit penalty.
• Itemized deductions: required in writing.
• Forwarding address: not a statutory condition of getting the deposit back.
• Penalty for wrongful withholding: Bad-faith failure to return or itemize exposes the landlord to twice the security deposit plus attorney's fees.
• Interest: Landlords with 25 or more units must pay interest on deposits held more than six months (765 ILCS 715).
• Small claims limit: $10,000.
• Statute: 765 ILCS 710/1 (Security Deposit Return Act).

Using both rules together

1. Read the lease for the deposit amount, the move-in date, and any clause that mentions the ordinance.
2. Check the local rule first: deposit cap under Cook County Code § 42-111, then paying the deposit in installments, return deadline and receipt and itemization.
3. Count the Illinois deadline of 45 days from termination of the tenancy.
4. A written demand that cites both 765 ILCS 710/1 (Security Deposit Return Act) and Cook County Code § 42-111 carries more weight than one that cites either alone. Bad-faith failure to return or itemize exposes the landlord to twice the security deposit plus attorney's fees.

Frequently Asked Questions

Q: Does Cook County require interest on security deposits?
A: The Residential Tenant and Landlord Ordinance (RTLO) does not add an interest rule, so Illinois law governs. Landlords with 25 or more units must pay interest on deposits held more than six months (765 ILCS 715).

Q: Is the Cook County deposit return deadline different from Illinois law?
A: Yes. Deposit must be returned within 30 days after the tenant vacates, with an itemized damage statement and paid receipts within 30 days if deductions are taken. Where the local rule is stricter than 765 ILCS 710/1 (Security Deposit Return Act), the stricter one is the one a landlord has to meet.

Q: Does the Residential Tenant and Landlord Ordinance (RTLO) apply to my unit?
A: Dwelling units in suburban Cook County. Municipalities with their own landlord-tenant ordinance (Chicago, Evanston, Oak Park, Mount Prospect) are excluded, as are owner-occupied buildings of six or fewer units, a single owner-managed single-family home or condo that meets four conditions, hotel and rooming-house stays under 32 days, institutional housing, co-ops and employee housing (42-102). Check the section cited below for the full list of exemptions before relying on it.

Q: Can I sue my landlord in small claims court for my Illinois deposit?
A: Yes. Illinois small claims court hears claims up to $10,000, which covers most deposits plus the statutory penalty. A dated written demand that cites 765 ILCS 710/1 (Security Deposit Return Act) is the usual first exhibit.

Sources Checked

• Cook County Code ch. 42, art. IV, §§ 42-101 to 42-114 (Ord. No. 20-3562, eff. 2021), Residential Tenant and Landlord Ordinance (RTLO): code text, read 2026-09-20
• 765 ILCS 710/1 (Security Deposit Return Act) (the Illinois statute cited above)
• LeaseLenses Illinois deposit data set, last reviewed 2026-09-19; the same data powers the Illinois demand letter tool
• Illinois landlord-tenant overview and the Illinois deposit rules page

This page is general legal information for Cook County, Illinois, not legal advice. Local ordinances are amended more often than state statutes; read the current code text before relying on a figure in court.