BulldogLowell:
FYI, regarding a US person importing and their obligations to US Customs.Get over $200 and you will start to see them get interested in your paying duties...
That is super useful. Thanks. I think the following information applies to the items that I have been "importing":
Personal vs. Commercial Use: Many import regulations only apply to goods imported for commercial - business or resale - purposes. For instance, most goods imported for personal use are not subject to quota. The one exception to this is made-to-measure suits from Hong Kong, which are subject to quota restrictions regardless of the use they are imported for. On the other hand, import restrictions that are based on health, safety and protecting endangered species apply across the board.
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The duty rate for many items typically bought in an on-line auction is zero, however, CBP may charge a small processing fee for mail imports that do require the payment of duty.
This explains exactly what I have been experiencing. Obviously, the situation in Belgium differs.