Guide8 min read · Updated July 2026
One code determines your duty rate, your taxes and your inspection risk. Here's how the Harmonized System works and how to get classification right the first time.
What is an HS code?
The Harmonized System (HS) is the global product-classification language of customs. Every product that crosses a border gets a code: the first 6 digits are identical worldwide, and countries extend them to 8–10 digits for their own tariffs. That code determines your duty rate, tax treatment, and whether permits apply.
How the code is structured
| Digits | Level | Example (men's cotton t-shirt) |
|---|---|---|
| 2 | Chapter | 61 - Knitted apparel |
| 4 | Heading | 6109 - T-shirts, knitted |
| 6 | Subheading (worldwide) | 6109.10 - Of cotton |
| 8–10 | National tariff line | Varies per country |
How to find the right code
- Start from what the product is, not what it's called commercially. Customs cares about material, function and construction.
- Apply the hierarchy: find the chapter, then the heading that describes the product most specifically.
- Check the legal notes. Chapters carry notes that include or exclude products in non-obvious ways (knitted vs woven apparel is the classic example: Chapter 61 vs 62).
- Verify the national extension for the destination country, that's where the actual duty rate lives.
What misclassification actually costs
- Overpaying duties for years without knowing it.
- Penalties and back-duties when an audit finds underpayment.
- Border delays when the description on your invoice doesn't support the declared code.
How BLS helps: we classify at line level from your product details, material, construction, use and keep the classification consistent across invoice, packing list and filings, shipment after shipment.
