The HS is a structured nomenclature comprising a series of four-digit headings, most of which are further subdivided into five- and six-digit subheadings. It was developed as a core system so that countries and organizations adopting it could make further national subdivisions according to their particular needs.

The HS provides a legal and logical structure within which, in terms of the 2017 version, a total of 1,222 4-digit headings, subdivided into 5,387 6-digit subheadings, are grouped into 97 chapters, the latter themselves arranged in 21 sections.

Each heading of the system is identified by a four-digit heading code, the first two digits of which indicate the chapter wherein the heading appears, while the latter two digits indicate the position of the heading in the chapter. The following examples illustrate the logical structure of the HS:

• The HS code for natural honey is 0409.00, which indicates that heading 04.09 has not been subdivided (fifth and sixth digits = 0);
• The HS code for buckwheat is 1008.10, which means that it is included in the first one-dash subheading (fifth digit = 1) of heading 10.08 and that this subheading has not been further subdivided (sixth digit = 0);
• The HS code for potato starch is 1108.13, which means that it falls in the third two-dash subheading (sixth digit = 3) of the first one-dash subheading (fifth digit = 1) of heading 11.08.