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How to read an HTS code

6 min read · updated 2026-11-12

An HTS number is not an arbitrary string. It is a path through a tree, and each block of digits is a level of that tree. Reading it that way is the difference between guessing at a code and being able to defend one.

The four levels

DigitsLevelExampleWho sets it
1–2Chapter61WCO (international)
3–4Heading6109WCO (international)
5–6Subheading6109.10WCO (international)
7–8Tariff line6109.10.00United States
9–10Statistical suffix6109.10.00.40U.S. Census / CBP

Take 6109.10.00 — cotton T-shirts. Chapter 61 is apparel and clothing accessories, knitted or crocheted. Heading 6109 is T-shirts, singlets and other vests, knitted or crocheted. The .10 subheading means “of cotton”. The two digits after that are where the US sets its own rate.

Why the first six digits matter more than the rest

The first six digits are identical in every country that uses the Harmonized System — over 160 of them. If a supplier gives you a six-digit HS code, it describes the same category of goods everywhere. The moment you add US digits seven and eight, you are in national territory, and another country's equivalent will not match.

That is why a Chinese supplier's “HS code” is useful for understanding the product category and useless for filing a US entry. The rate attached to a six-digit code is zero information: the six-digit level carries no duty rate at all. Rates live on eight-digit lines.

What actually decides the code

Not the product name. The General Rules of Interpretation (GRI) are a fixed sequence of tests, applied in order:

  1. GRI 1 — classify by the terms of the headings and any relevant section or chapter notes. Most classifications end here.
  2. GRI 2 — covers incomplete or unassembled goods, and mixtures.
  3. GRI 3 — when two headings both fit, the more specific description wins (3a); otherwise essential character (3b); otherwise last in numerical order (3c).
  4. GRI 4 — goods that cannot be classified otherwise go to the heading of their closest analogue.
  5. GRI 5 and 6 — packaging, and applying the rules at subheading level.
Chapter and section notes override the heading text. A product can look like it belongs in a heading and still be excluded by a note two pages earlier. Read the notes before you trust a description match.

The suffix is not free choice

The ninth and tenth digits split a tariff line for statistical purposes. They usually carry no separate rate, but they are not optional — CBP uses them to compile trade statistics, and an entry filed with the wrong suffix is still an entry with an error. On this site the suffixes are deliberately not given their own pages, because their rate columns are empty in the official schedule. Use them on the entry, not as a way to find a better rate.

A working procedure

  1. Describe the goods in customs language: material, function, whether assembled, whether a set.
  2. Find the chapter. If two chapters are plausible, read both chapter notes before choosing.
  3. Drop to the four-digit heading. Check section notes for exclusions.
  4. Apply GRI 3 if more than one heading survives.
  5. Take the six-digit subheading, then the eight-digit line, and read the rate columns.
  6. Check Chapter 99 and any Section 301 list separately — they are not in the rate columns.

If the answer is still ambiguous and the duty at stake is material, request a binding ruling from CBP. It is free, it is specific to your facts, and it is the only answer that protects you from a later reclassification.

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