215 ILCS 5/143b
Any insurance carrier whose payment to its insured is reduced by a deductible amount under a policy providing collision coverage is subrogated to its insured's entire collision loss claim including the deductible amount unless the deductible amount has been otherwise recovered by the insured, but if the deductible amount has been otherwise recovered by the insured it shall not be included in the subrogated loss claim and shall be excluded from the amount of loss pleaded. If the deductible amount is included in the subrogated loss claim the insurance carrier shall pay the full pro rata deductible share to its insured out of the net recovery on the subrogated claim. Administrative expenses of the insurance carrier cannot be deducted from the gross recovery, and only incurred expenses of the carrier, such as attorney's fees, collection fees and adjuster's fees, may be deducted therefrom to determine the net recovery. When the insurance carrier is recovering directly from a third party a claim by means of installments, the insured shall receive his full pro rata deductible share as soon as such amount is collected and before any part of such recovery is applied to any other use.
215 ILCS 5/143b