35 ILCS 200/21-335
Any person claiming interest or costs under Sections 21-315 through 21-330 shall include the claim in his or her petition for sale in error under Section 21-310, 22-35, or 22-50. Any claim for interest or costs which is not included in the petition is waived. Interest or costs may be awarded, however, to the extent permitted by this Section upon a sale in error petition filed by the county collector or municipality or upon a declaration by the county collector pursuant to subsection (c) of Section 21-310, without requiring a separate filing by the claimant. Any refund of interest or costs upon the petition for sale in error or upon a declaration by the county collector pursuant to subsection (c) of Section 21-310 shall be paid by the county treasurer as trustee of the fund created by this Section. The fund shall be the sole source for payment and satisfaction of orders for interest or costs, except as otherwise provided in this subsection. If the court determines that the fund has been depleted and will not be restored in time to pay an award with reasonable promptness, the court may authorize the collector to pay the interest portion of the award pro rata from those accounts where the principal refund of the tax sale purchase price under Section 21-310 is taken.
35 ILCS 200/21-335