35 ILCS 200/21-215: Penalty bids.

(a) Subject to subsection (b) of this Section, the person at the sale offering to pay the amount due on each property for the least penalty percentage shall be the purchaser of that property. No bid shall be accepted for a penalty exceeding 9% of the amount of the tax or special assessment on property.

(b) If the county offers to purchase property for the amount due in accordance with subsections (b) and (c) of Section 21-190, the county shall be the purchaser of the property notwithstanding any other offer. Subject to a payment plan implemented by the county clerk in accordance with subsection (d) of Section 21-385, the penalty bid for any property purchased by a county in this manner shall be 0.75% per month.