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.odes 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. These past codes are available on the World Customs Organization website as of May 2014, in their Publications section.