In reply to tom_in_edinburgh:
> It isn't tariffs that are the big cost. It's getting charged VAT twice because some EU suppliers can't be bothered to treat VAT differently for customers in the UK and the processing fees from the agent to clear the package through customs.
Bothered might not be the right word, first they need a notice from their tax authorities saying what the new system is and since the agreement is only provisional this may take some time, the taxman also has to read and understand the thousand odd pages!
Then there's the invoicing software which until a new version comes out automatically recognises the UK as still in the old system.
And then the slight hassle that the old EORI number (which identifies the exporter) that allows one to use the ATLAS system appears to be no longer valid as the UK is in another system. This makes it difficult to provide proof that the shipment was actually exported and without this the seller must apply VAT as if it was a domestic sale.