Substantial Transformation
The change that gives goods a new origin: a new name, character or use.
When materials from several countries are combined, the origin is the country where the last substantial transformation happened. The general test is whether the process produced an article with a new name, character or use.
In practice, customs applies it through a tariff-shift rule or a value-added threshold set for each heading. That is more predictable than the general test, and it is what a customs authority will actually check.
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