A property tax lien is a lien or claim for money due to a federal, state, or local government for unpaid and delinquent taxes. For example, the federal government may place a lien on a homeowner’s home or other real property for unpaid federal income taxes, and state and local governments (often counties) may place a lien on real property for unpaid income or property taxes.

The federal, state, or local government entity—also known as a taxing authority—may seek to recover payment for unpaid taxes by forcing the sale of the property on which the lien is placed in the foreclosure process—a process in which the validity of the lien and satisfaction (payment) for the lien is litigated or determined in court.

In California, a property tax lien represents a legal claim against a property by a governmental entity due to unpaid property taxes. When property taxes are not paid, the county tax collector can place a lien on the property. This lien has priority over most other liens or claims on the property, meaning it must be paid first if the property is sold. If the taxes remain unpaid, the taxing authority may eventually initiate a foreclosure process to sell the property at a public auction, known as a tax sale, to recover the owed taxes. The process is governed by California state law, specifically the California Revenue and Taxation Code. The foreclosure process involves court proceedings to ensure the lien's validity and to determine the payment for the lien. The property owner has the right to redeem the property by paying the full amount of taxes and penalties owed before the property is sold at the tax sale.