I work as a Customs broker and serve as the "go between" for CBP and importers. We don't know yet what it will look like. Refunds (if authorized) could be automatic like what happened when GSP was lapsed and renewed. It could be a manual filing process which is more likely under this administration. That is done via post summary correction (PSC) or protest. Both are generally follow one of two cost models - a % of the refund back or a flat fee. It shouldn't actually be too much administrative cost to the companies themselves.

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