How to read an HS code, digit by digit

An HS code reads left to right, from broad to specific. The first two digits are the chapter, the broad product family. Digits three and four are the heading. Digits five and six are the subheading, and those six digits are identical in every country that uses the Harmonized System. The United States then adds four more: digits seven and eight form the tariff line that legally carries the duty rate, and digits nine and ten are a statistical suffix that exists for trade data and never changes what you owe. So in 6109.10.00.12, a men's cotton t-shirt, the 16.5 percent duty attaches at 6109.10.00, and the .12 only tells the government it was a men's shirt.

That is the whole structure in a paragraph. The rest of this article covers what the digits do not tell you: how the rate columns work, how to read the indent structure without picking the wrong branch, and the handful of rules that decide which code is correct when two look plausible.

The digits, one segment at a time

The claim that duty attaches at eight digits is not a rule of thumb, it is written into the schedule. General Statistical Note 3 describes an article as "dutiable under subheading 0106.00.50," an eight-digit reference, and then explains that the ten-digit reporting number is formed by adding the two-digit suffix. General Statistical Note 2 goes further and states that the statistical annotations, meaning the two-digit suffixes and their descriptions, are not part of the legal text of the tariff schedule at all. You can see this in the data itself: 6109.10.00 shows a General rate of 16.5 percent, while its children .04, .07, .11 and .12 all have empty rate fields. They inherit the rate; they do not set one.

A detail that trips people up: when digits seven and eight are "00," as in 6109.10.00, that does not mean there is no duty. It means the US did not subdivide that international subheading any further for tariff purposes. The 16.5 percent still attaches there.

What sits above the chapter

Chapters are grouped into Sections, written in Roman numerals. The international Harmonized System has 21 sections and 97 numbered chapters, of which 96 are in use, because Chapter 77 is reserved for possible future use. Here is a distinction almost every article on this topic gets wrong: the US tariff schedule has 22 sections, not 21. Section XXII is a US-only addition covering special classification provisions and temporary legislation, and it holds Chapter 98 (special classification provisions such as US goods returned and repairs) and Chapter 99 (temporary modifications made under trade legislation). Chapter 99 is where the additional duties from trade actions live, which is why a Section 301 duty shows up on your entry as a second code in the 9903 series alongside the Chapter 1 to 97 classification.

Sections and chapters both carry legal notes, and those notes control classification. This matters more than beginners expect. The section and chapter notes routinely exclude goods you would confidently expect to find in a chapter and send them elsewhere. Chapter 39, for example, covers plastics, but its Note 2 pushes plastic furniture to Chapter 94, plastic toys to Chapter 95 and plastic handbags to heading 4202. The notes override intuition rather than supplementing it, which is why reading them is the first step rather than the last. The titles of sections and chapters, by contrast, are explicitly stated to be for ease of reference only.

Two codes read end to end

Take 6109.10.00.12. Chapter 61 is articles of apparel, knitted or crocheted. Heading 6109 is t-shirts, singlets, tank tops and similar garments. Subheading 6109.10 is "of cotton," and that is the last internationally shared level, so a cotton t-shirt is 6109.10 in Germany, Japan and Brazil too. The US line 6109.10.00 carries the General rate of 16.5 percent, a Special rate of Free for a list of free trade agreement partners, and a Column 2 rate of 90 percent. The suffix .12 means men's. The line also carries a footnote pointing to a Chapter 99 provision, which is how you learn that Chinese-origin goods on this line owe an additional Section 301 duty.

Now a technical one: 8517.13.00.00, smartphones. Chapter 85 is electrical machinery and equipment. Heading 8517 covers telephone sets including smartphones, and other apparatus for transmitting or receiving voice, images or data. Subheading 8517.13 is smartphones specifically, a dedicated subheading created in the 2022 edition of the Harmonized System, which is a good reminder that the nomenclature gets revised every few years as products change. The US line 8517.13.00 carries a General rate of Free and a Column 2 rate of 35 percent, and there is no further statistical breakout, so the suffix is .00.

The neighboring subheading makes the suffix point beautifully. 8517.14, for other telephones for cellular networks, splits into three statistical suffixes: .20 for vehicle-installed radio telephones, .50 for other public cellular service phones, and .80 for other. All three share one General rate of Free. Three different data buckets, one duty. That is exactly what the last two digits are for.

How to read the rate columns

The schedule shows three rate columns and importers misread them constantly.

Column 1 General is the normal trade relations rate, often called the MFN rate. It applies to goods from the large majority of countries and it is the default you pay if you claim nothing.

Column 1 Special holds reduced or free rates under free trade agreements and preference programs, shown as letter symbols in parentheses. The symbols are not intuitive. S is the United States, Mexico, Canada Agreement, which surprises people who expect something like CA or MX. Other common ones: AU Australia, CL Chile, CO Colombia, IL Israel, JO Jordan, JP the limited US Japan agreement, KR Korea, P the Dominican Republic and Central America agreement, PE Peru, SG Singapore, A the Generalized System of Preferences, D the African Growth and Opportunity Act. An asterisk on a symbol, like A* or E*, means some countries within that program are excluded for that specific line, so you have to read the general note rather than trusting the letter alone. A Special rate is a claim you make and must substantiate with origin evidence, not an automatic discount.

Column 2 holds the original 1930 statutory rates and applies only to countries without normal trade relations. General Note 3(b) currently lists exactly four: Belarus, Cuba, North Korea and the Russian Federation. The rates are punitive by design. That cotton t-shirt is 16.5 percent under Column 1 and 90 percent under Column 2.

Rates themselves come in three shapes. An ad valorem rate is a percentage of customs value, like the 16.5 percent above. A specific rate is an amount per unit regardless of value, like 1.9 cents per kilogram on oranges in 0805.10.00. A compound rate combines both. The best example in the whole schedule is wrist watches: subheading 9102.11.25 carries 40 cents each, plus 8.5 percent on the case, plus 14 percent on the strap, band or bracelet, plus 5.3 percent on the battery. One article, four separate valuations. If you have ever wondered why watch importers care so much about how a supplier itemizes an invoice, that is why, and it is covered in more depth on our HS codes for watches page.

The indent structure, and the mistake it causes

The printed schedule is a strict outline. Each additional dash means "this is a subdivision of the nearest line above it with one fewer dash." A line is read as its own text plus every superior line above it, concatenated. So 6404.11.20.30 is not simply "for men." It reads as sports footwear and similar, then having uppers of which over 50 percent of the external surface area is leather, then for men.

Two practical rules follow. First, a line ending in a colon is never a classification. It is a header that opens a subdivided list, and it has no rate of its own. Second, and this is where people go wrong, you must never compare across indent levels. You resolve one level completely, pick the winner, then descend into that winner's children only. Branches you did not pick are out of play permanently, and their more attractive-looking rates are irrelevant. This is not a stylistic preference; it is General Rule of Interpretation 6, which states that classification in subheadings is determined on the understanding that only subheadings at the same level are comparable.

Practically this means classification is a series of small binary decisions rather than a search for the best-matching description. If you find yourself scanning a chapter for the line whose words most resemble your product, you are doing it wrong and will usually land on a basket provision that does not apply.

The six rules that decide close calls

The General Rules of Interpretation apply in strict order. You may only reach a later rule when the earlier ones fail to resolve the question.

The US schedule adds its own Additional Rules of Interpretation on top. The two worth knowing cover principal use, where a "use" provision is controlled by the principal use of goods of that class in the United States, and actual use, which requires proof of the intended use within three years. There is also a rule that a "parts" provision does not prevail over a provision that specifically describes the part, which is the root of a great many parts classification disputes.

HS code, HTS code and Schedule B are three different things

An HS code is the six-digit international standard published by the World Customs Organization. It covers more than 5,000 commodity groups, is used by over 200 countries and economies, and accounts for the classification of more than 98 percent of world merchandise trade. No country charges duty at six digits. Those digits only guarantee that a smartphone is 8517.13 everywhere.

An HTS code is the ten-digit US import classification, published by the US International Trade Commission and enforced at entry by Customs and Border Protection. It takes the WCO's six digits verbatim, adds the legal tariff line at eight and the statistical suffix at ten. There are roughly 19,000 active codes and the schedule is revised several times a year. This is the number that goes on your entry summary. The difference is covered in full in our guide to HS code versus HTS code.

Schedule B is the ten-digit US export classification, published by the Census Bureau and reported through the Automated Export System. It shares the same first six digits but has a coarser national extension, roughly 9,000 codes against the HTS's 19,000, because exports need statistics rather than duty rates. Several HTS numbers often collapse into one Schedule B number. Useful asymmetry: a US company can generally use its HTS number in place of a Schedule B number when filing exports, but the reverse is never true. A Schedule B number is not valid on an import entry. We cover the distinction in HS code versus Schedule B.

Reading a code is not the same as choosing one

Everything above tells you how to decode a number someone hands you. Choosing the right number for a product you are about to import is a different job, and it is the one that carries liability. As importer of record you owe reasonable care on the classification even when a broker files on your behalf, so "our supplier gave us the code" is not a defense. Supplier-provided codes are worth exactly six digits anyway, since the last four are US-specific and your supplier has no reason to know them.

The practical workflow for a catalog of any size is to classify to six digits by product logic, then work the US subdivisions line by line using the indent rules above, and to keep a written rationale for each decision. That written record is what turns a classification into something defensible if CBP asks two years later, and if your product data already lives in a warehouse or database, it is worth being able to ask plain-English questions across the whole catalog rather than reclassifying by hand every season. Where the money is large or the call is genuinely close, a binding ruling from CBP converts your judgment into a decision that binds Customs at every port.

If you want the code without doing the outline work by hand, describe your product in the classifier at the top of this page and it will return the HS and HTS code with the reasoning behind it, or start from the category guides in our HS code lookup by product hub.