How to buy tax-sale property in Illinois (2026)

Illinois sells a tax lien certificate at the county collector's annual tax sale. The bid is not a price: bidders compete by offering the lowest penalty percentage, and the winner pays the amount due (delinquent taxes, assessments, interest and costs). Where a county uses an automated bidding system it accepts the lowest redemption price bid.

Source35 ILCS 200/21-355 (certificate amount / tax purchaser)35 ILCS 200/21-215

The penalty is the thing being auctioned. No bid may exceed 9 percent per penalty period, and the winning bidder is the one who will charge the least. The penalty stops accruing when the owner redeems.

Source35 ILCS 200/21-21535 ILCS 200/21-215

In counties with fewer than 3,000,000 inhabitants, registration is the default: at least 10 business days before the first day of sale, with a collector-set deposit of up to $250 (counties under 50,000 inhabitants) or $500. The deposit is applied to purchases and refunded to a registrant who attends but buys nothing. In counties with 3,000,000 or more inhabitants, the statute substitutes an irrevocable letter of credit or unconditional bond of at least 1.5 times the tax due (minimum $1,000). All bidders must personally attend.

• Representation and warranty form attesting compliance with the single bidder rule, included in each registration package in a county that has adopted a single bidder rule (21-205(b-5))
• A tax purchaser may not register more than one related bidding entity at the tax sale in a county with 275,000 or more inhabitants (single bidder rule, 21-205(b-5))
• County collectors may eject tax bidders who disrupt the tax sale or use illegal bid practices (21-205(c))

The owner has 30 months from the sale, except that vacant, commercial, industrial, multi-unit and 7-plus-unit property carries a shorter 12-month redemption under the registry exceptions.

Source35 ILCS 200/21-350

After the sale the purchaser holds a certificate of purchase, not a deed. If the owner does not redeem, the purchaser may complete the process to a tax deed. The registry carries the certificate step but no separate tax-deed citation beyond the statute the sale is built on, so treat the deed timeline as varying by county and confirm it with the collector.

Source35 ILCS 200/21-355 (certificate amount / tax purchaser)

Cook County is over 3,000,000 inhabitants, so the letter-of-credit rule above applies instead of a cash deposit, and the county must adopt a single bidder rule that bars one purchaser from registering more than one related bidding entity. The county registry records Cook's sale timing as "varies by county" and does not yet verify a platform.