A 10-digit HTS code looks like one long number, but it's really five nested levels stacked together — and each pair of digits does a different job. Learn to read those levels and a code like 6109.10.0012 stops being a mystery: it tells you what you're importing, what it will cost, and whether you even have the right code.

HTS stands for Harmonized Tariff Schedule — in the US, the Harmonized Tariff Schedule of the United States, or HTSUS. It's the master list that assigns every imported product a code, and that code drives your duty, your paperwork, and whether the goods clear at all. Getting it wrong is expensive; getting it right starts with being able to read it.

What Each Pair of Digits Means

Take a real code — 6109.10.0012, a men's cotton T-shirt — and read it from broad to specific. (The dots are only for readability; the code is ten digits.)

  • 61 — the Chapter. The first two digits drop the product into one of about 99 broad chapters. 61 is "articles of apparel and clothing accessories, knitted or crocheted."
  • 6109 — the Heading. The next two digits narrow it to a product family: 6109 is "T-shirts, singlets, tank tops and similar garments, knitted or crocheted."
  • 6109.10 — the Subheading. The next two digits get specific — .10 means "of cotton." This six-digit level is the international Harmonized System (HS) code, and it's identical in every country on earth. A factory in Vietnam, a broker in Germany, and US Customs all read 610910 as a cotton T-shirt.
  • 6109.10.00 — the US rate line. Digits seven and eight are where the schedule stops being international and turns American. This is the level that carries the actual duty rate.
  • 6109.10.0012 — the statistical suffix. The final two digits don't change your duty at all. They let the government track trade in fine detail. Here, "12" means men's cotton other T-shirts — the everyday printed and colored kind, as opposed to plain white undershirts, which sit under a different suffix.

The rule of thumb: the first six digits are global, the last four are American. The first six say what the product is; the last four say what the US charges and how it's counted.

From Six Digits to Ten: Building the Full Code

Here's the part that trips importers up. Your supplier almost always gives you just the six-digit HS number — 610910 — because that's all the rest of the world uses. US Customs needs all ten, and finding the other four is your job. It isn't guesswork; the schedule is a nested, indented list you drill down through:

  1. Open the subheading in the official schedule. Go to the US International Trade Commission (USITC) HTS at https://hts.usitc.gov and search or browse to 6109.10. Directly beneath the six-digit line, indented under it, are the US breakouts.
  2. Read the indentation as a decision tree. Each further indent narrows the category. Under 6109.10, the next split is by gender — "Men's or boys'" versus "Women's or girls'." Take the branch that fits your product.
  3. Land on your eight-digit rate line. Keep following the indents until you reach an eight-digit line with a duty rate beside it (6109.10.00). That rate is what you'll pay. If two lines could both fit, the more specific description wins.
  4. Pick the ten-digit statistical suffix. Beneath the rate line are the finest breakouts — men's versus boys', plain undershirts versus other tees. Match the most specific description: a men's printed cotton crewneck is "Other T-shirts: Men's," or 6109.10.0012.

One principle governs every branch you take: classify by what the product is, not by what you call it. That's the heart of the General Rules of Interpretation (GRIs), the ordering rules built into the schedule — the most specific description controls, and when a product could fit two places you classify by its essential character. A "performance hoodie" is still a knit cotton garment.

What the Code Actually Controls

Once you've pinned all ten digits, that code does real work:

  • Your duty rate. Rates sit in columns. Column 1 (General) is the standard rate for most trading partners; Column 1 (Special) is the reduced or free rate under free trade agreements (FTAs) and preference programs, if your goods qualify; Column 2 is a much higher rate reserved for a handful of countries. Your code sets the row; the country of origin picks the column.
  • Trade statistics. Those last two digits feed official US import data — the same data your competitors' shipments show up in. (See what your competitors' import records tell you.)
  • Admissibility. A code can flag that another agency has a say — food and cosmetics codes route to the FDA, for example. The HTS number is often what triggers those other-agency requirements at entry.

What the base code does not include: the extra tariffs that stack on top by origin — Section 301 on China, Section 232 on steel and aluminum, antidumping and countervailing duties. Those layer over your base rate. For how to total them, see how to research the tariff on your product.

Verify Before You Rely On It

The schedule shows you where a product could go; it doesn't prove you chose right. Two checks settle it:

  • CBP's CROSS database holds decades of real classification rulings on actual products. If something like yours has been imported, you can see how Customs classified it. Full walkthrough: how to search CBP's CROSS rulings database (or go straight to https://rulings.cbp.gov/home).
  • A binding ruling is CBP's legally binding answer for your specific product — worth requesting when the classification is ambiguous or the duty difference is large, at https://erulings.cbp.gov/s/. A licensed customs broker can also classify on your behalf.

HTS In, Schedule B Out

One common mix-up: the HTS is for goods coming into the US. When you export from the US, you use a different ten-digit code called Schedule B, maintained by the Census Bureau. Both grow from the same six-digit HS root, but the last four digits differ. Use the HTS for imports and Schedule B for exports — don't substitute one for the other on a customs filing.

The Part That's On You

The importer of record is legally required to use "reasonable care" in classifying goods, which means the code is your responsibility, not your supplier's. That six-digit number the factory sent is a starting point, not an entry code — and suppliers optimize for their side of the deal, not your duty exposure. Underpay because the code was wrong and you can owe back duties and penalties; overpay and nobody sends the difference back. The number you file is the number you answer for.

The Bottom Line

A 10-digit HTS code is readable once you see the layers: two digits for the chapter, four for the heading, six for the international subheading, eight for the US rate line, ten for the statistic. Start from your supplier's six, drill down the official schedule to all ten, verify against CBP's own rulings, and treat the classification as yours to defend — because at the border, it is.

This is general guidance, not legal or customs advice. Classification can turn on specific product details and the General Rules of Interpretation — confirm your codes with a licensed customs broker or a CBP binding ruling before you rely on them.

How do you assign HTS codes today — the number your factory gives you, your customs broker, the USITC tool, or a best guess — and have you ever had a classification challenged or corrected after the fact? We'd like to hear what it turned up.