My daughter recently bought an expensive light fitting from an American company. Apart from the shipping cost there was an option to insure against having to pay import/customs duty, it only cost about a pound so she ticked it. When it arrived I was asked to pay £24 duty which I did. Emailed them the receipt and was refunded 2 days later. Good service yes but surely you either have to pay duty or you don't which they must know.
Most small exporters blag the item with an under declaration with a low risk of there package being checked.
I once bought a lens from eBay from what was declared as a UK seller, when it arrived I had an import duty bill. But it was still only a quarter of what it should have been so I just paid it and put it down to experience.
I guess the low duty applied was down to a brief xray scan and a generic duty charge.
I would have thought that the sender was required to declare it if
duty was payable.
I think the responsibility is just to declare on the package what is contained and approximately what it's worth, they aren't expected to know tax import legislation in each country they dispatch to on such small value items. In this case they've undertaken to pay any costs incurred rather than simply adding a rider that any additional import duties incurred are your problem, which is nice.
As I understand it general rule of thumb at the post office is goods under £15 are ignored, anything that's over that if VAT is applicable they charge it and an inspection fee.
I've received several overseas packages that could have been charged but only been caught out once.