Reading an HTS code

Every article entered into the United States gets a ten-digit Harmonized Tariff Schedule number. The schedule is published by the US International Trade Commission, but the agency that decides whether your number is right is CBP: on the entry, on liquidation, or years later on an audit.

How the number is built

• Digits 1 to 2 are the chapter. There are 99, in 21 sections, running from live animals to works of art, with chapter 77 held in reserve.
• Digits 3 to 4 are the heading, digits 5 to 6 the international subheading. Those six are the Harmonized System proper, common to every country that uses it.
• Digits 7 to 8 are the US legal subheading. This is the rate line. The duty is set here, not further down.
• Digits 9 to 10 are the statistical suffix, there so trade data can be counted at finer resolution. They carry no duty rate, though getting them wrong is still an error.

That last distinction matters more than it sounds. Your supplier will give you a six-digit HS code from their own country. It is a starting point, not an answer. The US subheading beneath it is yours to determine and yours to defend.

Rules, not keyword search

The General Rules of Interpretation sit at the front of the schedule and are applied in order.

• GRI 1. Classification is determined by the terms of the headings and by the section and chapter notes. Most arguments end here, and most of the ones that go wrong went wrong because nobody read the notes.
• GRI 2(a). An incomplete or unassembled article with the essential character of the finished one is classified as the finished one. This is how a knocked-down machine is treated.
• GRI 3. When two headings both apply: the more specific description wins, failing that the material or component giving the goods their essential character, failing that the heading last in numerical order.
• GRI 5 and 6. Cases and packing follow the goods, and the same logic runs again one level down at the subheading.

The US then adds its own Additional Rules of Interpretation. The one that matters most separates a principal use provision, which asks what goods of that class are normally used for, from an actual use provision, which asks what you will do with them and wants proof.

Chapter 98 and Chapter 99

The last two chapters are where a modern entry gets complicated. Chapter 98 covers special classifications: American goods returned without advancement in value, articles assembled abroad from US components, and similar cases that cut duty when the documentary conditions are met.

Chapter 99 carries temporary modifications, and in 2026 it is where most of the money lives. Section 301 duties on Chinese-origin goods, Section 232 duties on metal content, and duties imposed under IEEPA all attach through subheadings in that chapter. A single entry line now routinely carries a Chapter 1 to 97 classification plus two or three Chapter 99 codes, and they stack. Read only the column 1 rate on the base line and you will underestimate the bill badly.

Where the money is actually decided

Three mechanisms do most of the damage, and none of them are visible in the base number.

Metal content.For derivative articles subject to Section 232, duty attaches to the value of the steel or aluminium content, reported on its own line, while the remaining value is classified normally. The origin that counts is where the steel was melted and poured or the aluminium smelted and cast, not where the article was made. So you need mill certificates from your supplier before the goods ship, and a bracket made in one country from another country's steel is not the duty answer it looks like.

Origin. For Section 301 and most trade remedies, origin turns on substantial transformation: whether processing created a new and different article with a different name, character and use. Screwdriver assembly does not shift origin, whatever the commercial invoice says.

Scope. Antidumping and countervailing duty orders are written as descriptions, not lists of HTS numbers, and the codes an order recites are stated to be for convenience only. Your goods can fall inside a scope even though your classification is not one Commerce mentioned. See the AD/CVD guide.

Where classification goes wrong

• Parts versus accessories. Section XVI note 2 and the corresponding notes elsewhere govern parts of machines, and they do not say what most people assume they say.
• Composite goods. Essential character under GRI 3(b) weighs bulk, quantity, weight, value and the role a component plays in the use of the article. Two reasonable people can disagree, which is exactly when you want the reasoning written down.
• Textiles. Chief weight and chief value rules mean a small change in blend percentage moves a garment to a different rate line.
• Copying the last entry. Products change. A supplier substituting a component or a resin moves the code without mentioning it, and the number on file quietly goes wrong across hundreds of entries.

Getting certainty

When the answer is genuinely arguable, ask CBP. A binding ruling under 19 CFR part 177 is a written determination that binds every port, and existing rulings are searchable in CROSS, the best free research tool an importer has. A ruling is prospective, so ask before the goods move.

The reason to bother is 19 U.S.C. 1592. A negligent violation exposes you to a penalty of up to twice the lawful duties of which the government was deprived, gross negligence up to four times, and fraud up to the domestic value of the merchandise. A valid prior disclosure made before CBP opens a formal investigation cuts that exposure sharply, which is why finding your own error is worth more than hoping nobody else does.

One last thing: the World Customs Organization revises the six-digit HS on a multi-year cycle, and the next edition moves a lot of codes. A classification you have leaned on for years is worth re-checking.