Abstract: A real property tax lien categorization and rating system and associated methods that facilitate classifications and ratings of tax liens from various counties of numerous states in the country, according to a common referenceable category scheme that facilitates identification of liens having common underlying real property characteristics, investment characteristics or other characteristics. In one example, a computer accesses a county server and its tax lien database via the Internet. The computer categorizes the tax liens, for instance into subgroups, and determines a rating for the tax liens based on one or more characteristics. The categorized tax lien information and the ratings of each tax lien are stored by the computer, for instance on one or more databases, so that this information is made available to third-party computers or computing devices (such as mobile devices or tablets) used by potential investors to evaluate the possible purchase of such tax liens.