Customs code, namely HS code, is the abbreviation of Harmonized Coding System. Its full name is the International Convention on the Harmonized Commodity Description and Coding System. HS adopts six-digit code, which divides all international trade commodities into 22 categories and 98 chapters. The following chapters are divided into order and subheadings. The first and second digits of the commodity code represent "chapter", the third and fourth digits represent "item", and the fifth and sixth digits represent "subtitle". The first six digits are HS international standard codes, and HS has four tax headings of 124 1 and six subheadings of 5 1 13. Some countries have divided seven, eight and nine figures according to their own reality.