An HS code is the classification number that tells customs what a product is. The Harmonised System, maintained by the World Customs Organization, sets the first six digits and is used worldwide. The European Union extends it to eight digits in the Combined Nomenclature and to ten in TARIC, where duty rates and import measures are attached.
Why the digits matter
The first six digits are the same everywhere, so they are what you agree with a counterparty. The additional digits are national or EU-level and decide the duty rate, whether a licence or quota applies, and whether a border control is triggered. Two products that look identical on a spec sheet can sit under different codes because of sugar content, preparation or packing.
Who is responsible
The declarant is legally responsible for the classification, not the seller who suggested it. If a classification is contested and the goods are already moving, the cost of the correction lands on the importer. For a recurring article it is worth obtaining a binding tariff ruling from the customs authority of the country of import rather than relying on a code copied from an old invoice.
Never treat an HS code found on a website as authoritative for your consignment. Confirm it with your customs broker and record who confirmed it.