If CBSA reassesses a shipment and finds the classification wrong, they come to you. Not to your supplier, not to your freight forwarder, and not — in any practical sense — to your customs broker. You are the importer of record. The declaration is yours.
That is the whole problem with copying the HS code off a commercial invoice. It feels like the supplier has done the work. They have done a piece of work, for their purposes, under their country's version of the nomenclature. Then it gets transcribed onto your accounting document and becomes your legal position.
How the code is actually built
The Harmonized System is a World Customs Organization nomenclature. Roughly 200 countries use it, which is why people assume an HS code is an HS code.
Only the first six digits are harmonized.
| Digits | What it is | Who sets it |
|---|---|---|
| 1–2 | Chapter | WCO |
| 3–4 | Heading | WCO |
| 5–6 | Subheading | WCO |
| 7–8 | Tariff item — this is what carries the duty rate | Canada |
| 9–10 | Statistical suffix | Canada (Statistics Canada) |
So your supplier in Shenzhen or Ho Chi Minh City can give you a perfectly correct six-digit code and it still tells you nothing about the Canadian tariff item. The duty rate, the free trade tariff treatment, and the permit requirements all live at the eight- and ten-digit level, in Canada's Customs Tariff.
Getting to that number is a legal exercise, not a lookup. You apply the General Rules for the Interpretation of the Harmonized System in order — Rule 1 first (the terms of the headings and the relevant Section and Chapter Notes), and you only move on when Rule 1 does not resolve it. Essential character under Rule 3(b) is not where you start. It is where you end up when the earlier rules have genuinely failed you. The WCO Explanatory Notes, CBSA's D10-series memoranda, and past Canadian International Trade Tribunal decisions are the interpretive material you reason with.
Why the supplier's code is the wrong code
Four reasons, and they compound.
It is an export code, built for an export purpose. In China, the export classification is tied to the VAT rebate the exporter receives. In the United States, exporters use Schedule B, which is a statistical export nomenclature, not the import tariff. The supplier's incentive is to pick the code that works for their side of the transaction. That is not corrupt; it is just a different question than yours.
National notes diverge even within the first six digits. Two countries can read the same subheading differently, and there is no central referee. A classification that is settled in the EU is not automatically settled in Canada.
The supplier does not know facts that change the answer. Classification frequently turns on end use, composition percentages, the state the goods are presented in at the border, whether something is a part or an accessory, or whether a multi-function machine has a principal function. Your supplier knows what they made. They do not necessarily know what you will do with it or how it will arrive.
Codes drift. A code gets keyed once, carries forward through every subsequent invoice, and nobody revisits it — even after the product spec changes, even after the WCO amends the nomenclature. The WCO revises the HS periodically, roughly every five years, and headings get split, merged, and renumbered. An old code can quietly stop existing.
There is a related trap in DDP arrangements, where the supplier arranges clearance and someone else's broker files on your behalf. The paperwork feels handled. It still generates a Canadian import record with consequences. If you are not sure who is on the hook for what, start with Incoterms and who actually carries the obligation.
Classification drives more than the duty rate
If duty were the only thing at stake, the exposure would be contained. It is not.
- Free trade preference. The rule of origin you have to satisfy under CUSMA, CPTPP or CETA is written against a tariff classification. Wrong code, wrong rule, and a certification of origin that does not actually support anything.
- Other government department requirements. Health Canada, CFIA, ECCC, Transport Canada and others attach their requirements to classification. A code that lands you in the wrong chapter can mean a permit you did not know you needed.
- SIMA. Anti-dumping and countervailing duties apply to defined goods described by classification. These are not small percentages.
- Surtaxes, quotas and remission orders. All keyed to the tariff item.
- Your landed cost model. If the duty line is wrong, your margin is wrong. Classification is an input to true landed cost, not an afterthought.
The self-assessment problem
Canada runs a self-assessment regime. CBSA does not check your classification at the time of release in any meaningful way. They check it later, during a verification, sometimes years later, and often by selecting a priority commodity and pulling every importer who declared it.
Two consequences follow.
First, release without issue means nothing. People take a clean import history as confirmation they are classifying correctly. It is not evidence of anything.
Second, the obligation runs the other way too. Under section 32.2 of the Customs Act, once you have reason to believe a declaration was incorrect, you have a limited window to file a correction — commonly cited as 90 days, but confirm the current wording before you rely on it. "Reason to believe" includes a ruling, a verification finding on a similar good, or a broker flagging an inconsistency. You cannot sit on it.
CBSA's reassessment reach goes back several years, and penalties under the Administrative Monetary Penalty System escalate with repeat contraventions. Under CARM, the reassessment lands directly on your own portal ledger, with your own payment obligation attached.
An illustration
Made-up numbers, to show the shape of the exposure. Say you import $400,000 a year of a product. You have been using a duty-free tariff item. CBSA concludes the correct item carries a rate of 7 per cent.
That is $28,000 a year in unpaid duty. Across a four-year look-back, $112,000, plus interest from the original accounting date, plus AMPS penalties, plus the GST that was under-collected on the higher duty-paid value. None of those are the real numbers for your goods — look up the actual rates for your candidate items — but the arithmetic is why a $900 question becomes a six-figure one if you leave it unasked.
The error runs both ways. Overpaying duty for years is just as common, and the refund window is shorter than the reassessment window.
When to ask for an advance ruling
CBSA issues advance rulings on tariff classification under section 43.1 of the Customs Act. The ruling binds CBSA for future importations of the goods described, it is free to request, and it is the only way to convert a judgement call into a settled position.
Request one when:
- Two candidate codes carry a material duty difference and you cannot clearly knock one out under the GIRs.
- The goods are composite, sets put up for retail sale, parts versus accessories, or machines with more than one function — the classic contested territory.
- Volume is high enough that a small rate difference becomes a large number over four years.
- The classification determines whether SIMA, a permit, or a quota applies.
- You are about to build a pricing model on an assumption you have not tested.
A thin request gets a thin answer. Expect to supply full technical specifications, a composition breakdown with percentages, photographs, exploded diagrams, the intended end use, lab reports where composition is contested, and your own reasoning with the GIR path you followed. If the ruling comes back against you, you have at least capped your exposure going forward and you know what to correct behind you.
Build a classification file
For each SKU, keep a one-page record: the technical description, the composition, the end use, the candidate codes you considered, the rule you applied to choose between them, the authority you relied on, who decided, and the date. Attach any ruling.
This does three things. It survives staff turnover. It gives a verification officer something to engage with other than your invoice. And it forces someone to actually reason through the decision rather than copy it. The same discipline you apply when you verify a new supplier belongs on the product side of the file.
Review the file when the product changes, when the supplier changes, and when the nomenclature is amended.
A broker can classify on your behalf and a good one is worth paying for. But the broker is working from the description you gave them, and the declaration carries your business number. Ask your broker how they arrived at each code. If the answer is that it came off the supplier's invoice, you have found the gap.