I worked closely with Custom's agents all over Europe including the UK, while I was a long hauler, I know how they, and their systems work, so it doesn't matter, that box is on their system because it incurred Import Tax, if I don't pay it or at least contact them within 28 days, my name and address will be flagged, and then I will get another letter demanding payment of the original amount and could also receive a penalty notice of up to £1000 fine, plus every box I get from anyone, anywhere outside the UK will be opened and examined, for the cost of 20 quid, simpler to just pay it.
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