Tax liens refer to a legal claim by a government authority, such as the IRS or state tax agency, against property owned by an individual or business that has failed to pay their outstanding taxes. The lien acts as security for the unpaid tax debt and allows the government to seize and sell the property if the taxes are not paid within a certain period of time. Tax liens can also impact credit scores, making it difficult for individuals or businesses with liens against their property to obtain loans or other forms of credit.