The law in plain English
Return deadline
Under 420 Ill. Comp. Stat. 46/20; 765 Ill. Comp. Stat. 710/1; 715/1 to 715/3, the deposit response usually has to be sent within 45 days of the move-out timeline described by the state rule.
Required notice
Illinois generally expects an itemized statement within 30 days and the deposit balance within 45 days after move-out.
This dispute type
Once the Illinois deadline passes, the dispute stops being only about the deductions and becomes a deadline-compliance problem too. A landlord may still argue damage existed, but 420 Ill. Comp. Stat. 46/20; 765 Ill. Comp. Stat. 710/1; 715/1 to 715/3 sets the clock for returning the balance and explaining any amount withheld.
Penalty leverage
If the withholding was wrongful or in bad faith, the exposure allowed under the statute is: You can recover up to two times the deposit amount as a penalty, plus court costs and attorney's fees