Ill. Admin. Code tit. 56, § 300.810
If, upon termination, an employee owes an amount greater than 15% of gross wages or final compensation, that amount may be withheld from the employee's wages or final compensation, but only if such an arrangement was included in the agreement signed when the advance was made.
(Source: Amended at 35 Ill. Reg. 12933, effective July 20, 2011)