The Harmonized Commodity Description and Coding System (HS) of tariff nomenclature is an internationally standardized system of names and numbers for classifying traded products developed and maintained by the World Customs Organization (WCO) (formerly the Customs Co-operation Council), an independent intergovernmental organization with over 170 member countries based in Brussels, Belgium.
Under the HS Convention, the contracting parties are obliged to base their tariff schedules on the HS nomenclature, although parties set their own rates of duty. The HS is organized into 21 sections and 96 chapters, accompanied with general rules of interpretation and explanatory notes. The system begins by assigning goods to categories of crude and natural products, and from there proceeds to categories with increasing complexity. The codes with the broadest coverage are the first four digits, and are referred to as the heading.