HS Code Structure: What the 6-10 Digits Actually Mean

You find a heading that matches your product. The description fits. You assign the code and move on.

Then customs rejects it. Not because the heading was wrong — but because a Note above the heading excluded your product from that entire chapter.

This guide breaks down how HS codes are structured, what each digit means, and why the Notes matter more than the headings themselves.

How is the HS code structured?

The Harmonized System (HS) is a classification framework maintained by the World Customs Organization (WCO). According to the WCO, over 200 countries and economies use this system, covering more than 98% of all merchandise in international trade.

The structure breaks down like this:

First 2 digits = Chapter (96 chapters in total; Chapter 77 is reserved for future use)
First 4 digits = Heading (approximately 1,228 headings)
First 6 digits = Subheading (over 5,600 subheadings)

These 6 digits are universal. The same 6-digit code means the same product in Seoul, New York, Hamburg, and Sydney.

After 6 digits, each country adds its own extensions. The United States extends to 10 digits under its Harmonized Tariff Schedule (HTS). The EU uses 8 to 10 digits under the Combined Nomenclature (CN). Korea uses 10 digits under its own tariff schedule. These additional digits determine the actual duty rate applied at your border.

What are Section and Chapter Notes — and why do they matter?

Section and Chapter Notes are legal provisions printed before the headings in every tariff book. Under GRI Rule 1 — the first of six General Rules of Interpretation set by the WCO — these Notes carry legal authority. The titles of Sections and Chapters are for reference only.

In the WCO's own words: classification must be determined "according to the terms of the headings and any relative Section or Chapter Notes." The titles are explicitly labeled as non-binding.

This means a heading description can look like a perfect match for your product — and still be wrong. If a Note excludes your product, that heading does not apply. Period.

According to customs law firm Braumiller Law Group, classification audits have revealed cases where companies had up to 80% incorrect classification on their products, sometimes persisting for years without detection.

Can you give a real example of Notes overriding a heading?

Yes. Consider a steel filing cabinet. It is made entirely of steel. Steel is a base metal. Section XV of the HS is titled "Base metals and articles of base metal." The heading description fits.

But Section XV, Note 1(k) explicitly excludes articles of Chapter 94 — which covers furniture. A filing cabinet is furniture. So it cannot be classified under Section XV, regardless of its material.

The correct classification: Chapter 94, not Section XV.

Here is another example. A copper necklace — base metal, clearly. Section XV covers base metal articles. But Section XV, Note 1(e) excludes goods of Chapter 71, which includes imitation jewelry. The necklace goes to Section XIV, Chapter 71.

Both examples follow the same pattern:

Material points to one chapter
Note excludes it
Function or product type sends it elsewhere

This distinction matters for your tariff rate. According to U.S. customs law, negligent misclassification can result in fines up to 20% of the goods' domestic value. Fraud can trigger penalties up to 4 times the unpaid duties. And CBP can audit entries going back 5 years.

What happens after 6 digits?

The first 6 digits are set by the WCO. Every member country uses the same 6-digit subheading. After that, national authorities add digits based on their own tariff and statistical needs.

Take HS 8471.30 — portable computers. That subheading is the same everywhere. But the full 10-digit code differs:

Korea: 8471.30.1000
United States: 8471.30.0100

Both are correct in their own country. Neither applies in the other's. This is why you cannot copy your supplier's full 10-digit code onto your import entry. The first 6 digits transfer. The rest must be reclassified under your country's tariff schedule.

According to the WCO, the HS is organized into 21 Sections across those 96 Chapters. Goods in Chapters 1 through 83 are generally classified by material. Goods in Chapters 84 through 96 are generally classified by function. Understanding this split helps you navigate the structure faster.

How do the 6 General Rules of Interpretation (GRI) work?

The WCO established 6 General Rules of Interpretation (GRI) that must be applied in order when classifying any product. You cannot skip to Rule 3 without first applying Rule 1.

Here is a simplified breakdown:

GRI 1: Classify by heading terms and Section/Chapter Notes. Titles are not legally binding.
GRI 2: Incomplete, unfinished, or disassembled goods can be classified as the finished product if they have its essential character.
GRI 3: When a product fits two or more headings, classify under the most specific description. For sets, classify by essential character.
GRI 4: If Rules 1-3 don't resolve it, classify under the heading most akin to the product. Rarely used.
GRI 5: Cases, containers, and packaging are generally classified with the product they hold.
GRI 6: Rules 1-5 apply again at the subheading level. Only subheadings at the same level are comparable.

Most classification disputes come down to GRI 1 and GRI 3. If you get GRI 1 right — reading the headings and the Notes — you avoid most common errors.

How do you verify your HS code before importing?

Before assigning an HS code, follow this checklist:

Identify your product's function, material, and intended use — all three can affect classification
Find the relevant Section and Chapter — use the table of contents as a guide, not as a classification basis
Read the Section Notes — check for exclusions before looking at headings
Read the Chapter Notes — check for definitions and scope limitations
Match the heading terms — compare your product against the legal text, not just the title
Apply GRI in order — if the heading terms and Notes don't resolve it, move to GRI 2, then 3
Check national extensions — reclassify beyond 6 digits using your destination country's tariff schedule
Request a binding ruling for recurring items — US has CROSS, EU has BTI, Korea has 품목분류사전심사

One ruling now saves you from audit surprises later. The WCO updates the HS every 5 years — the current edition took effect January 1, 2022, with the next revision expected in 2027. Codes that were correct last year may not be correct today.