If you move final assembly out of China to cut tariff exposure, the label on the box is not a marketing choice. For goods entering the United States, country of origin is a legal determination. Marking it wrong is a customs problem; claiming a third-country origin when the product was only screwed together there is how “China+1” turns into a detention. This piece covers how the marking rule actually works, when assembly changes origin and when it does not, and what to ask a factory before you print “Made in Vietnam.”
1. What the marking rule requires — before you talk about tariffs
Under 19 U.S.C. 1304 and 19 CFR part 134, most imported articles must be marked with the English name of the country of origin, in a conspicuous place, as permanently as the product allows, so the ultimate purchaser can see it. “Made in China” and “Product of China” are the usual forms. A US address on the same package triggers an extra rule: the origin marking must sit close to that address, in comparable size, so a California warehouse address does not look like a US-made claim.
Origin for this purpose is the country of manufacture, production, or growth. If more than one country is involved, further work in the last country must amount to a substantial transformation — a new article with a new name, character, or use — before that last country becomes the origin.
2. The test that decides China vs Vietnam (or Thailand, Mexico, etc.)
Substantial transformation is not a percentage of invoice value, and it is not “we have a factory in Vietnam.” CBP looks at the process as a whole. Recent rulings keep drawing the same line:
- Simple assembly of Chinese parts in a third country usually stays Chinese origin. Inserting a finished Chinese mechanism into a housing, or bolting together kits whose essential character was already set in China, has been held not to transform the article.
- Real manufacturing in the third country can shift origin. CBP has found a third-country origin where the plant makes the character-defining part there — for example, SMT production of the main circuit board that functions as the device’s “brain,” or fabricating and welding a vehicle frame from plate and tube rather than assembling a knockdown kit. In those fact patterns, later pack-out in China did not pull origin back to China.
The same facts can go either way. That is why CBP rulings are written as applying only to the specific merchandise described. A supplier’s statement that “everyone marks these Made in Vietnam” is not a ruling.
3. Marking origin and duty origin are related — and still easy to mix up
For most China-to-US shipments that are not claiming a free-trade preference, the substantial-transformation test is also the test CBP uses for Section 301 and similar tariff measures. If the origin is still China, the China tariff stack applies even if the last screw was turned in Vietnam. If CBP agrees the third country substantially transformed the good, the marking and the Section 301 analysis typically follow that country.
Do not assume FTA rules (USMCA tariff-shift tests, for example) are the same as the marking test. Preference programs have their own recipes. Marking still has to match the origin CBP will accept for that entry.
4. What this means on the factory floor
A China+1 plan that only adds a packing line, a paint booth, or a final screw-together station is the weakest fact pattern. CBP has treated that kind of last-step work as insufficient. In NY N361910 (2026), a finished Chinese hydraulic-breaker body assembled into a third-country housing stayed Chinese origin, because inserting the character-defining mechanism into a shell did not create a new article.
Where CBP has accepted a third-country origin, the plant was making the part that gives the product its character. In HQ H350697, SMT production of the main circuit board in Vietnam was enough for a smartwatch to be marked as a product of Vietnam even though final assembly and pack-out were in China. In NY N357652 (2026), fabricating and welding an e-bike frame in Thailand from tube stock made Thailand the origin, even though the bike was assembled in China. NY N340936 reached a similar result where a UTV frame and chassis were manufactured and welded in Vietnam rather than assembled from a knockdown kit.
Those holdings are model- and process-specific. Component origin still matters, and a third-country plant that only imports finished Chinese subassemblies is arguing uphill. Do not treat another importer’s ruling as a template for your SKU.
5. What to do before you print the mark
- Map the bill of materials by country — not just the last factory address. Which part gives the finished good its name, character, or use?
- Describe the third-country process in operations, not slogans. “Assembled in Vietnam” is not enough. Welding a frame from tube, SMT of a blank board into a functioning PCBA, and snapping two housings together are different facts.
- Do not copy another importer’s mark. Ask whether the supplier has a CBP ruling on this model, or whether you should request one through counsel before a large program. Rulings are model- and process-specific.
- Keep production evidence. If CBP questions origin, they want process sheets, photos, BOMs, and value-add — not a brochure.
- If a US address is on the retail pack, put the origin marking next to it. That is a frequent, avoidable marking violation.
The bottom line
Country of origin is not the country on the commercial invoice and not the country of the last warehouse. For US marking — and usually for China-specific tariffs — it is where the article last became a new product. Simple assembly of Chinese components in Vietnam, Thailand, or Mexico generally does not get you “Made in Vietnam.” Making the character-defining part there might. Get the process straight before you print the label; changing a mark after a detention is much more expensive than asking the question at sampling.
Origin and marking rules are in 19 U.S.C. 1304 and 19 CFR part 134. Holdings cited include NY N361910, HQ H350697, NY N357652, and NY N340936; each applies only to the facts described in that ruling. Substantial-transformation outcomes can differ from FTA preference rules. Confirm the current regulation and, where the duty stake is large, consider a binding ruling before relying on a third-country mark. General guidance, not legal or customs advice.