Amends the Property Tax Code. Makes changes concerning interest penalties due on delinquent amounts in counties with 3,000,000 or more inhabitants beginning in tax year 2023. Specifies that counties shall be the designated holders of all tax liens and certificates that are forfeited to the State or county. Makes changes concerning sales in error and forfeited tax certificates in provisions concerning the assignment of tax certificates; databases of properties available for sale; scavenger sales; forfeited tax liens and certificates; records of forfeitures; payments for property purchased at tax sales; certificates of purchase; refunds of costs; redemption of properties; special assessments; partial settlements; notices; and the issuance and contents of deeds. Provides that, in the case of a sale in error because of an error by the assessor, chief county assessment officer, board of review, board of appeals, or other county official, the error must be material to the tax certificate at issue. Provides that, in the case of a sale in error because of a bankruptcy, provides that the bankruptcy case must be open on the date the collector's application for judgment was filed. Provides that, in Cook County, service of process may be made by a person who is licensed or registered as a private detective (currently, those provisions apply in counties other than Cook). Makes other changes.