305 ILCS 5/10-13.7
The fees of witnesses for attendance and travel shall be the same as the fees of witnesses before the Circuit Court of this State; such fees to be paid when the witness is excused from further attendance. When the witness is subpoenaed at the instance of the Illinois Department or any employee thereof, the fees shall be paid in the same manner as other expenses of the Illinois Department. If the witness is subpoenaed at the instance of any other party to the proceeding, the Illinois Department may require that the cost of service of the subpoena or subpoena duces tecum and the fee of the witness be borne by the party at whose instance the witness is summoned. In such case, the Illinois Department may require a deposit to cover the cost of such service and witness fees.
305 ILCS 5/10-13.7