The Harmonized Commodity Description and Coding System, also known as the Harmonized System (HS) of tariff nomenclature is an internationally standardized system of names and numbers to classify traded products. It came into effect in 1988 and has since been developed and maintained by the World Customs Organization (WCO) (formerly the Customs Co-operation Council), an independent intergovernmental organization based in Brussels, Belgium, with over 200 member countries.
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. First, the system assigns goods to sections, and then proceeds to assign these goods to their specific chapter, heading, and subheading], in that order, as necessary. The HS therefore assigns up to a total of 8 digits at the tariff-rate (legal) level. Two extra digits may also be assigned as statistical reporting numbers for a total of 10 digits to be listed on entries.
To ensure harmonization, the contracting parties must employ at least 4- and 6-digit provisions, international rules and notes, but are free to adopt additional subcategories and notes. Chapter 77 is reserved for future international use only. Chapters 98 and 99 are reserved for national use. Chapter 98 comprises special classification provisions, and chapter 99 contains temporary modifications pursuant to a parties' national directive or legislation.
All products can be classified in the HS by using the General Rules for the Interpretation of the Harmonized System ("GRI"). Product codes can be determined according to their form and function. An example of a product classified according to its form would be whole potatoes. The classification will also change depending on whether the potatoes are fresh or frozen. Fresh potatoes are classified in position 0701.90, under the Header Potatoes, fresh or chilled, Sub header Other, while frozen potatoes are classified in position 0710.10 under the Header Vegetables (uncooked or cooked by steaming or boiling in water), frozen, Subheader Potatoes.
An example of a product classified according to its function would be an electric resistance-heated oven. The classification for an electric oven depends on whether the oven is for domestic or industrial use. An electric oven for domestic use is classified in position 8516.60 under the Header Electric instantaneous or storage water heaters and immersion heaters; electric space heating apparatus and soil heating apparatus; electro-thermic hairdressing apparatus and hand dryers; electric flatirons; other electro-thermic appliances of a kind used for domestic purposes; electric heating resistors, other than those of heading 8545; parts thereof, Subheader Other ovens; cooking stoves, ranges, cooking plates, boiling rings, grillers and roasters. Industrial electric ovens are classified in position 8514.10 under the Header Industrial or laboratory electric furnaces and ovens (including those functioning by induction or dielectric loss); other industrial or laboratory equipment for the heat treatment of materials by induction or dielectric loss; parts thereof, Subheader Resistance heated furnaces and ovens .
These rules apply to all products. Any product for which there is no current classification can be listed under the Other classification. This term encompasses all products described by the Header and Subheader of a category. The potatoes in the first example fall into this category, as they can also describe genetically modified potatoes, which were not available during the elaboration of the first HS.
As of 2015, there were 180 countries or territories applying the Harmonized System worldwide,
- Customs tariffs
- Collection of international trade statistics
- Rules of origin
- Collection of internal taxes
- Trade negotiations (e.g., the World Trade Organization schedules of tariff concessions)
- Transport tariffs and statistics
- Monitoring of controlled goods (e.g., wastes, narcotics, chemical weapons, ozone layer depleting substances, endangered species)
- Areas of Customs controls and procedures, including risk assessment, information technology and compliance.
Codes have been revised through the years. If it is necessary to refer to a code used in a past trade issue, contracting parties must refer to the definition used at the time of the agreement. 
Challenges in classification for companies
Companies may face classification issues when creating new products due to the possibility that an invention can belong to several categories or sub-categories at once. Later, it may be costly to correct an improperly classified product.
Improper classification may also cause products to be delayed at international borders. Classification helps determine if there are any export/import licensing requirements between countries; for example, if these products have any restrictions, they may be seized at border crossings. In the United States, Export Administration Regulations must deal with products crossing the border. A slight difference in classification can create a big difference in the taxes that are paid.
- Automated Export System
- Broad Economic Categories
- Combined Nomenclature
- Customs tariff
- Harmonized Tariff Schedule for the United States
- Standard International Trade Classification
- TARIC Coding System
- World Customs Organization
- Why HS codes are important
- ITC's Product Conversion Table on Market Access Map, an online database of customs tariffs and market requirements. The table allows you to search for product codes by name and convert them into any HS revision.
- World Bank's list of HS Codes products
- World Bank, Concordances from HS to other nomenclatures
- HS Code Search Database by Foreign Trade Online
- EU Combined Nomenclature Search Engine by European Commission - Eurostat
Tariffs by region
- Customs Tariff of Canada (Canada Border Services Agency)
- European Community Common Customs Tariff TARIC
- German Electronic Customs Tariff EZT-online
- Indian Harmonized System Code
- Irish Customs and Excise Tariffs
- Japan Tariff Association – webpage refers to Japan Harmonised System Code Search
- Mexico import-export codes (Harmonized Tariff Schedule) by SIICEX and CAAAREM
- UK Tariff Codes Datasets by Data.Gov.UK
- Official Tariff Book of South Africa (South African Revenue Service)
- United States of America