A property tax lien is a legal claim against the property of an individual or business that fails to pay taxes owed to the government. By purchasing the tax lien at a tax lien auction you are purchasing the tax debt owed to the city or parish. This gives the buyer certain rights to gain interest and penalties on the amount of the original auction. As a tax lien holder you also have the obligation to maintain the property taxes left unpaid and ongoing. Interest and penalties are accrued on those paid taxes as well.