35 ILCS 200/20-178
When the county collector makes any refunds due on certificates of error issued under Sections 14-15 through 14-25 that have been either certified or adjudicated, the county collector shall pay the taxpayer interest on the amount of the refund at the rate of 0.5% per month.
No interest shall be due under this Section for any time prior to 60 days after the effective date of this amendatory Act of the 91st General Assembly. For certificates of error issued prior to the effective date of this amendatory Act of the 91st General Assembly, the county collector shall pay the taxpayer interest from 60 days after the effective date of this amendatory Act of the 91st General Assembly until the date the refund is paid. For certificates of error issued on or after the effective date of this amendatory Act of the 91st General Assembly, interest shall be paid from 60 days after the certificate of error is issued by the chief county assessment officer to the date the refund is made. To cover the cost of interest, the county collector shall proportionately reduce the distribution of taxes collected for each taxing district in which the property is situated.
This Section shall not apply to any certificate of error granting a homestead exemption under Section 15-170, 15-172, 15-175, 15-176, or 15-177.
35 ILCS 200/20-178