The customs tariff used by most countries worldwide. It was formerly known as the Brussels Tariff Nomenclature and is the basis of the commodity coding system known as the Harmonized System. 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. The HTS therefore sets forth all the international nomenclature through the 6-digit level and, where needed, contains added subdivisions assigned 2 more digits, for a total of 8 at the tariff-rate line (legal) level. Two final (non-legal) digits are assigned as statistical reporting numbers if warranted, for a total of 10 digits to be listed on entries.