The Harmonized System (HS) is the international product nomenclature developed and maintained by the World Customs Organization. More than 200 countries use it as the basis for their customs tariffs and trade statistics, covering over 98% of world trade.
The HS is organized into 21 sections and 99 chapters, with each product assigned a 6-digit code. The first two digits identify the chapter, the next two the heading, and the final two the subheading. Countries then extend the 6-digit code with additional digits for national tariff and statistical purposes — the U.S. uses 10 digits (HTS), the EU uses 8 (CN code) or 10 (TARIC).
The WCO revises the HS every five years to reflect changes in trade patterns and technology. Recent editions include HS 2017 and HS 2022. The next revision, HS 2028, is currently under negotiation.
Because the first 6 digits are universal, an HS classification in one country generally aligns with the same classification in another — making the HS the backbone of international trade statistics and free trade agreement rules of origin.