How to Read an HS Code: Structure, Format and Classification Explained
- John Hall
- Customs Specialist at iCustoms.ai
Every HS code contains more information than most traders realise. Those six digits are not a random sequence. They follow a precise, logical hierarchy that moves from the broadest product category down to the most specific description. Once you understand that structure, any HS code becomes readable.
This guide covers the HS code format in full, from the 21 sections at the top of the hierarchy down to the six-digit subheading, with a worked example, a walkthrough of the WCO General Rules of Interpretation, and a country-by-country comparison of how national tariff systems extend the international standard.
The HS Code Format: Six Digits, Three Levels
The HS Code format is built on a six-digit numbering system divided into three two-digit segments. Each segment narrows the product description from a broad category to a specific classification. This format is identical in every country that uses the Harmonized System, which covers over 200 countries and more than 98% of world merchandise trade.
| Digits | Level | Name | What It Identifies | Number in the System |
| 1 to 2 | Level 1 | Chapter | The broadest product category (e.g., Chapter 61 = knitted clothing) | 96 Chapters |
| 3 to 4 | Level 2 | Heading | A specific product group within the chapter (e.g., 6109 = T-shirts) | Approximately 1,200 Headings |
| 5 to 6 | Level 3 | Subheading | A precise product description within the heading (e.g., 6109.10 = of cotton) | Approximately 5,600 Subheadings |
The six-digit subheading is the internationally standardised element that all countries share. Anything added beyond digit six is a national extension specific to each country’s customs system. These extensions carry information about duty rates, quotas, and trade measures that apply within that country.
HS Code Structure Example: Reading 6109.10 Step by Step
The best way to understand the hs code structure is through a worked example. Take HS code 6109.10, which covers cotton T-shirts. Here is how to read it digit by digit.
| Code | Classification Breakdown |
|---|---|
| 61 |
Chapter 61: Articles of apparel and clothing accessories, knitted or crocheted Digits 1–2 (Chapter) |
| 6109 |
Heading 6109: T-shirts, singlets and other vests, knitted or crocheted Digits 3–4 (Heading) |
| 6109.10 |
Subheading 6109.10: Of cotton Digits 5–6 (Subheading) |
Starting from the left, digits 6 and 1 place the product in Chapter 61, which covers all knitted and crocheted clothing. Digits 0 and 9 identify Heading 6109 within that chapter, specifically T-shirts and similar garments. Digits 1 and 0 form the subheading 6109.10, which specifies that the garment is made of cotton.
A UK trader importing cotton T-shirts would use the full 10-digit commodity code 6109100010, extending the six-digit HS subheading with national digits that identify the applicable UK duty rate and any relevant trade measures.
A Second Example: HS Code 0203.12
For a product from a different part of the tariff, take HS code 0203.12, which covers frozen hams and shoulders of swine with bone in.
| Digits | Code | Description |
|---|---|---|
| 1 to 2 (Chapter) | 02 | Chapter 02: Meat and edible meat offal |
| 3 to 4 (Heading) | 0203 | Heading 0203: Meat of swine, fresh, chilled or frozen |
| 5 to 6 (Subheading) | 0203.12 | Subheading 0203.12: Frozen hams, shoulders and cuts thereof, with bone in |
The same reading logic applies regardless of the product. Chapter first, then heading, then subheading. The hierarchy always moves from broad to specific.
The Hierarchy of HS Codes: Sections, Chapters, Headings and Subheadings
What is the hierarchy of HS codes? The Harmonized System is organised into four levels, each sitting within the one above it. The full structure of the HS code system is as follows.
| Level | Name | Count | Description |
|---|---|---|---|
| Level 0 (Top) | Sections | 21 Sections | The highest organisational level, grouping related chapters together. Sections are not part of the code itself and provide context for the chapters they contain. |
| Level 1 | Chapters | 96 Chapters | Two-digit codes (01–97, with 77 reserved). Each chapter covers a broad product family. For example, Chapter 01 covers live animals, while Chapter 97 covers works of art. |
| Level 2 | Headings | ~1,200 Headings | Four-digit codes formed by adding two digits to the chapter number. Headings identify a specific type of product within a chapter. |
| Level 3 | Subheadings | ~5,600 Subheadings | Six-digit codes that form the internationally standardised HS classification system. Subheadings are the building blocks used in customs declarations worldwide. |
The 21 Sections are groupings that sit above the chapter level. Section I covers live animals and animal products (Chapters 01 to 05). Section XI covers textiles and textile articles (Chapters 50 to 63). Section XVII covers vehicles, aircraft, vessels, and associated transport equipment (Chapters 86 to 89). Sections do not appear in the HS code itself but are used in the Chapter and Section Notes that govern classification decisions.
The 96 Chapters each cover a distinct product family. Chapter numbers run from 01 to 97, with Chapter 77 currently reserved for future use. Within each chapter, headings break down the product types further, and subheadings add the final layer of precision that makes the six-digit code specific enough for global use.
How Are HS Codes Classified?
The process of assigning an HS code to a product is called tariff classification. How are HS codes classified? Classification follows a defined legal framework set by the WCO, known as the General Rules of Interpretation (GRI). These six rules are applied in order and provide the legal basis for every classification decision made by customs authorities worldwide.
In practice, classification begins with an analysis of the product: what it is made of, how it is made, what it is used for, and how it is described in the tariff schedule. The trader or customs broker then works through the HS hierarchy, starting at the chapter level and narrowing down through headings and subheadings until the correct six-digit code is identified.
General Rules of Interpretation: How HS Code Classification Works
The General Rules of Interpretation of the Customs Tariff (GRI) are the legal framework used to classify goods under the Harmonized System. The WCO publishes these rules as part of the official HS Convention. There are six rules, applied in strict order. Rule 1 must be considered before Rule 2 is consulted, and so on.
For the majority of goods, classification is resolved by GRI 1 alone. The remaining rules exist to handle more complex situations such as unfinished goods, mixtures, sets, and goods that could logically appear under more than one heading.
| Rule | Name | What It Covers | When It Applies |
|---|---|---|---|
| GRI 1 | Section, Chapter and Heading Notes | Classification is determined by the terms of the headings and any relevant section or chapter notes. Headings are read in the context of their legal notes. | Applies first, for all goods. Most goods are classified under GRI 1 alone. |
| GRI 2(a) | Incomplete or Unfinished Articles | An unfinished or incomplete article is classified in the same heading as the complete article, provided it has the essential character of the complete article. | Applies to kits, components, and partially manufactured goods. |
| GRI 2(b) | Mixtures and Combinations | Mixtures or combinations of materials or substances are classified as if they consisted of the material that gives them their essential character. | Applies to composite goods and products made from multiple materials. |
| GRI 3(a) | Most Specific Description | When goods could be classified under two or more headings, the heading with the most specific description takes precedence over a more general heading. | Applies when GRI 2 leaves two or more potential headings. |
| GRI 3(b) | Essential Character | Composite goods or sets are classified by the material or component that gives the whole its essential character. | Applies to retail sets and composite goods where GRI 3(a) fails to resolve classification. |
| GRI 3(c) | Last in Order | When neither GRI 3(a) nor GRI 3(b) resolves classification, use the heading that occurs last in numerical order among those under consideration. | Rare. Final tie-breaker within GRI 3. |
| GRI 4 | Most Akin Goods | Goods that cannot be classified under GRIs 1 to 3 are placed in the heading appropriate for the goods to which they are most similar. | Applies to genuinely novel products not described anywhere in the schedule. |
| GRI 5(a) | Cases and Covers | Cases, covers, and containers designed for specific articles and sold with them are classified with those articles. | Applies to instrument cases, tool boxes, and similar packaging sold as part of the product. |
| GRI 5(b) | Packing Materials | Packing materials are classified with the goods they contain, unless they are clearly suitable for repetitive use. | Applies to packaging and wrapping materials. |
| GRI 6 | Subheading Comparison | At the subheading level, classification is determined by comparing subheadings at the same level within the same heading. GRIs 1 to 5 apply by analogy. | Applies after the heading is determined, to choose between subheadings. |
The WCO General Rules of Interpretation are published in the official HS Convention and in the Explanatory Notes to the Harmonized System. HMRC applies these rules in all UK tariff classification decisions. For advance classification certainty, UK traders can apply to HMRC for a Binding Tariff Information (BTI) ruling. |
How to Understand an HS Code in Practice
The most reliable way to understand how to understand hs code classification is to follow the same process used by HMRC classification officers. Start by describing the product accurately: what it is made of, how it is manufactured, and its primary use. Then identify the most likely chapter using the Section and Chapter Notes of the UK Trade Tariff. Work through the headings in that chapter until you find the one that best describes the product. Finally, compare subheadings within that heading, applying GRI 6, to reach the six-digit subheading.
If the product could plausibly fall into more than one heading, GRI 3(a) requires you to choose the heading with the most specific description. A heading that names the product explicitly always takes precedence over a heading that covers a broader class of goods in which the product might also be included.
HS Code Countrywise: How National Systems Extend the International Standard
The six-digit HS subheading is the same in every country that uses the Harmonized System. Beyond six digits, however, each country builds its own national extension to carry information relevant to its own customs and trade policy. This is what is meant by hs code countrywise variation.
| Country or Region | National Code Name | Total Digits (Import) | National Extension (Beyond 6 Digits) | Administered By |
|---|---|---|---|---|
| United Kingdom | Commodity Code | 10 Digits |
Digits 7–8: Combined Nomenclature (CN) alignment. Digits 9–10: UK-specific tariff rates and trade measures. |
HMRC / UK Trade Tariff |
| European Union | TARIC / CN Code | 10 Digits |
Digits 7–8: Combined Nomenclature. Digits 9–10: EU trade measures, anti-dumping duties, quotas, and suspensions. |
European Commission / DG TAXUD |
| United States | HTS Code | 10 Digits |
Digits 7–8: US statistical suffix. Digits 9–10: Trade measure identifiers, including anti-dumping duties, safeguards, and preference claims. |
USITC / CBP |
| Canada | Customs Tariff Number | 10 Digits |
Digits 7–8: Canadian statistical categories. Digits 9–10: National tariff treatment codes. |
Canada Border Services Agency |
HS Schedule B Code Structure: The US Export Classification System
In the United States, the HS Schedule B code structure is used for export classification. Schedule B codes are 10-digit codes managed by the US Census Bureau. The first six digits of a Schedule B code are identical to the international HS subheading. The remaining four digits are US-specific and used for trade statistics.
Schedule B codes are distinct from HTS codes, which are used for US imports and managed by the United States International Trade Commission (USITC). Both systems share the same six-digit HS foundation but apply different national extensions for imports and exports respectively. This is the US equivalent of the UK’s use of 10-digit codes for imports and 8-digit codes for exports.
Where to Find the HS Code List
The complete hs code list is maintained and published by the WCO and is also reproduced in the national tariff schedules of every country that uses the Harmonized System. For UK traders, the primary reference tools are as follows.
| Resource | What It Contains | Where to Access |
|---|---|---|
| UK Trade Tariff | Full UK commodity code list for imports (10 digits) and exports (8 digits), with duty rates, measures, and guidance notes | trade.gov.uk/import-goods / trade.gov.uk/export-goods |
| WCO Harmonized System Database | The complete international HS nomenclature with explanatory notes, legal texts, and classification opinions | wcoomd.org (subscription required for full access) |
| EU TARIC Database | The full EU customs tariff with 10-digit TARIC codes, duty rates, and EU trade measures | ec.europa.eu/taxation_customs/dds2/taric |
| USITC HTS Database | Complete US Harmonized Tariff Schedule with 10-digit HTS codes and duty rates for all US imports | hts.usitc.gov |
| iCustoms iClassification | AI-powered classification tool that matches product descriptions to the correct UK commodity code from the UK Trade Tariff | icustoms.ai/iclassification |
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