What are the General Rules of Interpretation,
and how do they work?

What the GRI actually are

The General Rules of Interpretation, usually shortened to GRI, are six legal rules published as part of the Harmonized System by the World Customs Organization. They exist for one purpose: to settle which HS code applies when the heading text alone does not make it obvious, so that two different people classifying the same product arrive at the same answer.

Most products never need more than the first rule. A heading describes the item plainly, no section or chapter note excludes it, and the code is settled. The GRI matter most for the harder cases: products made of more than one material, sold unfinished or unassembled, packaged as a set, or genuinely resembling more than one heading at once. Rather than leaving those calls to instinct, the GRI apply in a strict, non-negotiable order.

They are called "general" because they sit above any individual chapter or heading. Whatever product is being classified, whatever chapter it eventually lands in, the same six rules govern how that decision gets made.

Why the GRI matter

Skipping the GRI, or applying them out of order, is one of the most common ways a classification goes wrong. Each rule is only meant to be reached once the one before it has failed to settle the question, and jumping ahead tends to produce a code that looks reasonable but would not survive a closer review.

If a rule is misapplied	What tends to happen
Skipping GRI 1's section and chapter notes	A heading that looks correct on its face gets used, even though a note explicitly excludes the product.
Reaching for "essential character" too early	GRI 3(a)'s more specific description gets bypassed in favor of a judgment call that was never supposed to be needed.
Treating GRI 3(c) as a shortcut	The "last in numerical order" tie-breaker gets used as a default, when it is meant only for genuine ties nothing else resolves.
Applying GRI 2 to complete, finished goods	Rules meant for unfinished or unassembled articles get used on products that never needed them, muddying the reasoning trail.

A code produced this way can still clear customs without incident for years. The risk shows up later, when an audit or a broader review traces the reasoning back and finds the rules were applied out of sequence.

The six rules, in order

The GRI apply in strict numerical order. A later rule is only relevant once every rule before it has failed to produce an answer. Here is what each one covers, roughly summarized:

Applying the rules in practice

The GRI are not something a classifier chooses to invoke. They apply automatically, in sequence, every time. What changes is how far into the sequence a given product needs to go before an answer emerges.

In plain terms, the decision process usually looks like this:

GRI 3 is where most of the real judgment happens. Its three sub-rules only apply in order: 3(a) asks whether one heading describes the product more specifically than the others, and if so, that settles it. Only if 3(a) fails to decide does 3(b) ask which material or component gives the product its essential character. Only if that also fails does 3(c) fall back to whichever heading comes last in numerical order. It sounds procedural, and it is meant to. The whole point is to remove personal judgment from as much of the process as possible.

Common mistakes when applying the GRI

GRI vs. Explanatory Notes vs. rulings

The GRI rarely operate alone. Two other sources of guidance sit alongside them, and it helps to know which one carries actual legal weight versus which one is a reference tool.

Source	Legal status	Used for
General Rules of Interpretation	Legally binding	The core framework that determines which heading and subheading a product falls under.
Explanatory Notes	Persuasive, not binding	WCO commentary illustrating how the GRI have been applied to specific kinds of goods; widely relied on but not law itself.
National rulings	Binding for the party that requested it	A customs authority's written determination on a specific product, such as a US CBP ruling, which can be cited as precedent for similar goods.

In practice, classifiers work through all three: the GRI to determine the legal process, the Explanatory Notes to see how similar products have been reasoned through before, and existing rulings to check whether a customs authority has already ruled on something close to the product in question.

Getting started

If your company is applying the GRI for the first time, a few habits make the process far less error-prone:

• Always start at GRI 1. Read the heading text and every relevant section and chapter note before considering any later rule.
• Work through GRI 3's sub-rules in order: specific description, then essential character, then numerical order, never out of sequence.
• Write down which rule settled the classification, not just the resulting code, so the reasoning can be defended later.
• Check the Explanatory Notes and any existing rulings on similar products before finalizing a genuinely ambiguous case.

The GRI reward patience more than expertise. Most disputes trace back to a rule that was skipped or applied out of order, not to a genuinely novel product. Work through the sequence properly, and the harder cases become far more manageable.