Why HS codes matter for machined parts
I once watched a shipment of stainless steel valve bodies sit in customs for nine days because the commercial invoice listed a general hardware HS code instead of the specific valve-parts classification. The duty rate difference was not enormous, but the delay cost the buyer an expedited air freight upgrade to avoid a production line stoppage. Getting the HS code wrong is one of the most avoidable causes of customs delays on CNC machined parts.
The Harmonized System (HS) is a six-digit numerical classification maintained by the World Customs Organization. Individual countries extend these to 8-10 digits for their own tariff schedules. The code determines the import duty rate, whether any trade remedies or restrictions apply, and how customs evaluates the declared value against risk profiles.
How the six-digit framework works
An HS code reads from general to specific. The first two digits are the chapter, the next two narrow to a heading, and the final two pinpoint the subheading. For example, Chapter 76 covers aluminum articles; heading 7616 is other aluminum articles; subheading 7616.99 covers other articles of aluminum not elsewhere specified. Beyond six digits, each country adds its own national tariff lines.
- Digits 1-2 (chapter): broad product category such as Chapter 76 (aluminum), Chapter 73 (iron/steel articles), or Chapter 84 (machinery/mechanical appliances)
- Digits 3-4 (heading): product group within the chapter
- Digits 5-6 (subheading): specific product type
- Digits 7-10: national subdivisions, varying by country (e.g. 10-digit HTSUS in the US, 8-digit CN code in the EU)
Common HS chapters for CNC machined parts
Most precision machined parts fall into a handful of chapters, depending on material and function. Below are common starting points, but final classification depends on the specific part, its material composition, and its intended use.
| Chapter | Covers | Typical parts |
|---|---|---|
| Chapter 73 | Articles of iron or steel | Stainless steel fasteners, brackets, shafts, general machined steel parts |
| Chapter 76 | Aluminum articles | Aluminum spacers, housings, flanges, heatsink components |
| Chapter 74 | Copper articles | Copper connectors, bushings, electrical contact parts |
| Chapter 84 | Machinery and mechanical appliances | Machine parts, valve components, pneumatic and hydraulic parts |
| Chapter 85 | Electrical machinery and equipment | Motor components, electrical connector parts, sensor housings |
The above are common reference points only. Final classification is subject to the ruling of the importing countrys customs authority, and we strongly recommend confirming the code with your freight forwarder or licensed customs broker before shipping.
Why classification gets tricky with precision parts
A machined part can be classified based on its material (such as an article of steel under Chapter 73) or based on its function (such as part of a machine under Chapter 84). Customs generally follows the essential character principle: if a part has a specific, dedicated function in a machine, it may classify under that machines heading rather than as a general article of the material.
- Multi-material parts: a steel shaft with a brass bushing may need classification by the material that gives essential character
- Parts for a specific machine vs. general hardware: dedicated valve components often fall in Chapter 84 (valves) rather than Chapter 73
- Surface treatment: anodizing or plating does not generally change classification, but confirm with your broker
- Prototype vs. production: the classification follows the part as described, regardless of batch size
How to confirm the right code before shipping
Ask your supplier to list the HS code on the proforma invoice, but do not accept it blindly. Suppliers classify based on Chinese export codes, which may differ at the 8-10 digit level from your import countrys code. Cross-check with your customs broker or forwarder, ideally sending them a part drawing or photo and a description of the end use. For high-volume or high-value shipments, consider a binding tariff ruling from your customs authority, which locks in the classification for that specific part.
Final classification is subject to the ruling of the importing countrys customs authority. Always verify with your freight forwarder or licensed customs broker before the goods ship. A few hours of broker review upfront is far cheaper than a customs hold or duty reassessment after arrival.
Frequently Asked Questions
Can the same part have different HS codes in different countries?
Yes. The first six digits are harmonized globally, but digits 7-10 are national. The same aluminum housing might fall under different national subdivisions in different countries. Confirm the full code for the destination country.
What happens if I use the wrong HS code?
Possible outcomes include clearance delays, duty reassessment with back-payment, penalties for misdeclaration, or in severe cases seizure of goods. Underpayment of duties may also trigger audits on future shipments.
Should I let my supplier choose the HS code?
Ask for their code as a starting point, but verify with your own broker. Chinese export classifications are optimized for export clearance, not necessarily for import compliance in your country.
Do prototypes need HS codes?
Yes. All commercial shipments crossing borders require an HS code on the customs declaration, regardless of value or purpose, though low-value samples may use simplified procedures depending on the destination country.
Is there a database to look up HS codes?
Most customs authorities maintain online tariff databases (e.g. USITC HTSUS for the US, TARIC for the EU). These help narrow down options but do not replace broker review for complex or ambiguous parts.