USPAP is the Uniform Standards of Professional Appraisal Practice. USPAP is published and maintained by the Appraisal Standards Board (ASB) of the Appraisal Foundation, a non-governmental entity charged by Congress with promulgating appraisal standards.
USPAP is revised periodically, usually every year. It begins with a list of Definitions, and a Preamble defining the mission. It then declares a set of general Rules governing all disciplines of appraisal practice: The Ethics Rule, the Competency Rule, the Scope of Work Rule, the Jurisdictional Exception Rule, and the Supplemental Standards Rule. It then sets forth 10 appraisal Standards, each containing a number of Standards Rules. Each Standard covers in detail the different tasks an appraiser might perform in the course of developing and reporting an appraisal ("Real Property Appraisal Development"; "Real Property Appraisal Reporting"; "Business Appraisal, Development"; etc.). It includes a number of Statements on those 10 appraisal Standards, some retired, which are used to clarify or supplement the Standards. It also includes Advisory Opinions dealing with the application of the USPAP in various scenarios, such as "When does USPAP apply in valuation services?" and "Clarification of the client in a federally related transaction," which describe real-life problems and how they would be governed under the Rules and Standards of USPAP.
Every appraiser is charged with knowing and following USPAP, usually by operation of state law, and must complete Continuing Education periodically to relearn the basics and become familiar with new Advisory Opinions and annual changes to USPAP. USPAP may be considered the Bible of appraisal practice.