The way I understood it, is that EU-to-EU shipments are affected by the packaging registration requirement and fee, along with shipments from outside the EU. It's not technically an import duty (which is not applied to EU-to-EU shipments).
"Packaging registration requirement and fee"? Never heard of that... But I´m not a sales-expert.
When I buy something in another E.U.-memberstate and have it shipped to me, I only pay the purchase-price plus the shipping-cost.
There might be some/a lot of confusion due to Brexit though, especially in the southern area of the E.U.
I know some Playmobil sellers in e.g. ... (well, you know) who were informed by their local postal offices, that they now have to include custom-documents with every package shipped to e.g. Germany or the Benelux-countries. False information they got from their confused local postal services due to Brexit, it still is only necessary when shipping outside the E.U. At least that is what I get told here by my local postal and custom sources
What can happen, is that sometimes a webshop - usually the big international platforms like e.g. Amazon (and also a certain Geobra Brandstätter) but only rarely a local shop - takes into account the (very) small difference in VAT-tax that exists between member-states (e.g. 21% VAT in Belgium, 20% VAT in France and 19% VAT in Germany) and adjusts the sales-prices (once you registered or entered your address) to the VAT applicable in the country you reside in, but like I said most shops don´t that. When one crosses the border physically to purchase something in another E.U-country, then on the return-trip there is also no custom-agent waiting (anymore) behind the bushes (growing on the former borders) to charge the (usually) small VAT-difference.
Meanwhile, Germany still wants invoices in duplicate, which creates more packaging to be trashed. (That's an extra plastic envelope and two sheets of paper.)
I think it should be in triple, with one for the courrier-company responsible for handling the imported goods and two for the receiver of the goods. Of course only for packages coming from outside the E.U.
Import duties are not handled by states in the US. They're determined and charged when the package reaches the country (not the destination state)
Same here, as I was once informed. Or it should be, if rules are interpreted and applied correctly.
Clear as mud?