The WCO Explanatory Notes are the official interpretation of the Harmonized System (HS) at international level. They are not part of the HS Convention and are not legally binding, but customs authorities, tribunals and courts use them to decide what a heading covers, and in many classification disputes they settle the outcome. They cannot override the legal text: the headings and the Section and Chapter Notes come first.
The HS itself is the nomenclature, developed and maintained by the World Customs Organization (WCO), that customs administrations use to classify goods. Disputes over where a product belongs can lead to duty demands, penalties and shipment delays. This article explains what the Explanatory Notes are, how much legal weight they carry, how they are used in disputes, and where they fall short.
What the Explanatory Notes are
The Explanatory Notes are published by the WCO, approved by the WCO Council, and issued in five volumes with amending supplements. They follow the structure of the nomenclature: general notes for Sections and Chapters, a note for each heading, and subheading notes where needed. There are also Explanatory Notes to the General Rules for the Interpretation (GRIs, called GIRs in some tariffs).
In practice they do three things:
- Explain the scope of broad or ambiguous heading texts.
- Give examples of goods that a heading includes.
- List exclusions, which mark the boundary between headings and often point to the heading that does apply.
How much legal weight they carry
The WCO itself says the Explanatory Notes do not form an integral part of the HS Convention but constitute the official interpretation of the HS at the international level. The legal texts are the headings, the Section, Chapter and Subheading Notes, and the GRIs; GRI 1 says classification is determined “according to the terms of the headings and any relative Section or Chapter Notes”. The difference between these layers is set out in the legal anatomy of HS classification.
National courts give the Explanatory Notes considerable, though not binding, weight. In the United States, the Court of Appeals for the Federal Circuit has described them as “not legally binding” but “generally indicative of the proper interpretation” of the tariff, for example in Chemtall, Inc. v. United States, 878 F.3d 1012 (Fed. Cir. 2017). In India, the Supreme Court has long treated the HSN Explanatory Notes as a safe guide to the meaning of tariff expressions, and restated that position in May 2026 in the n-hexane dispute analysed in When a Solvent Looks Like a Fuel.
Because of that weight, a business can cite the Explanatory Notes in an appeal or a reply to a customs query to support its reading of a heading, and a classification that follows them is easier to defend.
Why classification disputes arise
- The scope of a heading or subheading is unclear, and the importer and customs read it differently.
- Product descriptions are inconsistent or vague, or use technical or marketing terms that do not match the tariff wording.
- Importers, exporters and customs officers start from different assumptions about what the product is.
- New products, such as advanced electronics and composite materials, do not fit headings written before they existed.
How the Explanatory Notes help settle disputes
Where a heading text is broad, the Explanatory Note usually says what it includes and gives examples. Where two headings compete, an exclusion in one note often names the other heading and ends the argument. The instant noodle soup case study shows an exclusion in an Explanatory Note deciding between pasta and soup preparations.
The Explanatory Notes to the GRIs also explain how each rule is meant to work, for example what “essential character” means under GRI 3(b), which helps keep the rules applied consistently. The rules themselves are explained in the practical guide to the GRIs.
Two examples
Smartwatches: Chapter 85 or Chapter 91
Whether a smartwatch is a communication apparatus of heading 85.17 or a wrist-watch of heading 91.02 has been argued in several countries. An earlier version of this article said the Explanatory Notes resolved the question in favor of Chapter 85 on the basis of primary function. That was an oversimplification. The outcome depends on the product and is decided under GRI 1 and GRI 3, with the Explanatory Notes and WCO classification opinions as guidance. The European Union’s Implementing Regulation (EU) 2024/964 placed one smartwatch, imported as a retail set, in CN code 9102 12 00: no principal function could be identified, so GIR 3(c) gave the heading last in numerical order. The regulation distinguished it from the article in HS Classification Opinion 8517.62/23. Other smartwatches, which only relay data to a paired phone, have been classified in subheading 8517.62. The smartwatch case study compares a Canadian and a US ruling that reached different headings.
Food supplements: medicament or food preparation
Nutritional supplements are often contested as pharmaceuticals (Chapter 30) or food products. Here the legal note comes first: Note 1(a) to Chapter 30 excludes “foods or beverages (such as dietetic, diabetic or fortified foods, food supplements, tonic beverages and mineral waters)”, other than nutritional preparations for intravenous administration. The Explanatory Notes then help place the supplement within the food chapters, through their descriptions and examples of preparations and their composition.
Where the Explanatory Notes fall short
They are international guidance, and national practice can still differ: tariffs add their own notes and subdivisions below six digits, and national authorities and courts reach different conclusions on the same goods, as the smartwatch example shows. They are updated with each HS edition and through amendments, but new technology can still get ahead of them. And for difficult goods they are rarely enough on their own; classification opinions, national rulings and specialist advice fill the gap.
Most importantly, an Explanatory Note cannot contradict a heading or a legal note. Where the two conflict, the legal text wins.
Using the Explanatory Notes well
- Use the edition that matches the HS edition in force (HS 2022 today; HS 2028 from 1 January 2028), and track the amending supplements.
- Read the heading text and legal notes first, then the Explanatory Note, and cite both in your classification record.
- Train staff to read the exclusions as carefully as the inclusions.
- Use software that brings the Explanatory Notes into the classification workflow, but check its output against the text.
- Get specialist advice for complex or high-value classifications.