The Harmonized System code is the international numerical taxonomy that classifies every traded product. The first 6 digits are globally standardized under the World Customs Organization. Countries extend it to 8 or 10 digits for their own duty schedules. In the US, the 10-digit code is called the HTS (Harmonized Tariff Schedule) code. In Canada, it’s the 10-digit CCT (Canadian Customs Tariff). The first 6 digits are always the same across countries.
How it works in practice
A practical example: a brand sells a women’s cotton t-shirt. The 6-digit HS code is 6109.10. The US HTS extends that to 6109.10.0027 (women’s cotton t-shirt, knit). The base MFN duty rate on that code is 16.5%. With USMCA qualification, the rate drops to 0%. Without USMCA, the Section 122 surcharge stacks on top.
Classification is harder than it sounds. The difference between 6109.10 (t-shirts) and 6105.10 (men’s shirts) is often a single design element, but the duty rates differ by several percentage points. Misclassifying products is the most common cause of CBP audit findings, and the importer is liable for back-duty plus penalties going three years back.
Why it matters
The HS code on every entry is the foundation of duty calculation. Get the code wrong and you either overpay duty (bad for margin) or underpay duty (bad for compliance, with interest and penalties on audit). For brands with hundreds of SKUs, a one-time HS classification project pays for itself within months by catching misclassifications and identifying USMCA-eligible codes.
Common misconceptions
- HS codes are not interchangeable across countries beyond the first 6 digits. The US HTS-10 and Canadian CCT-10 are different numbers.
- A vendor invoice description is not a substitute for a classification. CBP audits on the actual code, not the freight bill description.
- Software auto-classification (sometimes called “AI classification”) can be wrong on edge cases. A trained customs broker or classification specialist still beats automated tools on novel products.