735 ILCS 5/12-708
The garnishee is entitled to assert against the indebtedness due to the judgment debtor offsetting claims against either or both the judgment creditor and the judgment debtor, whether due at the time of service of the garnishment summons or thereafter to become due and whether liquidated or unliquidated, except claims for unliquidated damages for actions sounding in tort. To the extent that other property belonging to the judgment debtor or in which the judgment debtor has an interest is pledged to or held by the garnishee in good faith as security or that the garnishee has other just claim against the other property, the garnishee is entitled to retain the other property. The garnishee is liable for the balance of the indebtedness due to the judgment debtor after the offsetting claims are adjusted and for the balance of other property after deducting property to which the garnishee has just claim. The verdict or finding and judgment shall show the amount of offsetting claims or deductions allowed against each party.
735 ILCS 5/12-708