735 ILCS 5/12-122
Any defendant, his or her heirs, executors, administrators, assigns, or any person interested in the premises, through or under the defendant, may, except as to any sale had by virtue of a judgment of foreclosure in accordance with Article XV of this Act, within 6 months from the sale, redeem the real estate so sold by paying to the purchaser thereof, his or her heirs, executors, administrators or assigns or to the sheriff or other officer who sold the same, or his or her successor in office, for the benefit of such purchaser, his or her heirs, executors, administrators, or assigns, the sum of money for which the premises were sold or bid off, with interest thereon at the rate of 10% per annum from the time of such sale, whereupon such sale and certificate shall be null and void. If there has been a prior redemption by a judgment creditor, his or her heirs, executors, administrators or assigns, then redemption by a defendant, his or her heirs, executors, administrators or assigns, or any person interested in the premises through or under the defendant, shall be in accordance with Section 12-137 of this Act.
735 ILCS 5/12-122