Taiwanese exporters are being warned that a "Made in Taiwan" stamp does not guarantee US customs will treat a product as Taiwanese, a risk for firms that assemble goods from Chinese parts.

• Origin is decided by the importing country's customs, not the exporting country, so Taiwan's rules carry no weight at the US border.
• The US has no fixed formula for what counts as real transformation and judges case by case, even when the work happened in Taiwan.
• More goods now use Chinese materials finished in Taiwan, which puts this third-country processing question under a spotlight.
• The White House recently named Taiwan among 40-plus economies where Chinese goods might be rerouted to dodge US tariffs.
• A suspected origin-laundering case at circuit board maker Unimicron lands at an awkward moment for Taiwan-US trade talks.

Outlook: Taiwan faces growing pressure to prove its supply chains are clean, and exporters are being told to check US rulings or seek advance origin decisions before shipping.