This was done for one reason, and one reason only. To avoid building more customs infrastructure. It's that simple.
What are they going to do when a company collects the VAT and doesn't pay it to HMRC and decide to keep it for themselves as a nice 20% bonus?
I think Borises actually want to offload the collection at the point of sale on
a UK outlet.
Now, this would kind of work if it was still 1950ies of the last century, but the way we do retail changed since then. Many major outlets are just handlers or drop shippers.
So - let's say I manufacture oak wood computer cases somewhere in the forests of Germany. Because I prefer full control over retail prices for my boutique product rather than wholesale I manage all my sales outlets by myself. Today I want to sell ten of my cases, worth £200 each via Amazon to UK customers. I'm already DE VAT payer, but EU VAT exchange no longer works within UK. Today I have to register for UK VAT number with HMRC and two EORI numbers, one for Europe and one for UK.
Once I ship my oak PC cases over to Amazon UK, using my GB VAT number and UK EORI, the moment my 10 cases arrive in Kent depo I am liable for £400 of UK VAT, which Amazon has to immediately collect and pay over to the HMRC. Keep in mind that this VAT is on top of the declared value of my merchandise, not my actual sales or earnings less Amazon fees. Any tiering of prices or volume discounts will no longer be possible to my Amazon UK customers because I have to know the sale price right here, right now and declare it to HMRC straight away. I also don't think it's yet clear if Amazon will provide me with line of credit or some other arrangement, but obviously in the worst case scenario it involves international money transfers before I actually make a sale. After each of my cases actually sell on Amazon Prime, and selling fees are deducted, I will also have to register my sale with DE VAT, and pay that to my taxman. And then I guess, somehow try to deduct UK VAT as a "cost of sale", but because there is no existing mechanism to offset one against the other - who knows at this point. In short - whichever way I take it - each item from my made up German company shipped towards UK generates: custom form, pre-emptive/pre-sale VAT invoice, me owing 20% straight away to HMRC, someone collecting it for me, and then the usual chain of taxes inside of my own country.
So, right from the get go, my best bet to stop bleeding money into multiple VAT chains and freezing both assets and money upfront for months is to stop exporting to UK. Stop shipping anything to Amazon UK immediately and not to sell anything to UK customers via web with direct shipments. Which is something we are going to see literally within days this week.
Instead, just as my grandfathers did before me, I'd have to wait for some importer from UK to come to me, buy my product and physically take it away to UK customers. Obviously I would have to sell to that importer at a retail price I used to charge, because why would I earn any less. Right? That way I only pay DE VAT as if it were local sales and UK importer handles all the unregulated mess of bureaucrats from London (see what I did there?) on their own. However, because the chain is back to what it was 100 year ago - my product is immediately at least 20% more expensive to UK customers - as UK retail price is on top of the DE retail price + DE VAT, plus whatever handling fees. But how is that my problem as a fantasy German oak PC case manufacturer?
So, you see, this isn't a free trade agreement of any kind. It only gives us no customs duty. This free trade agreement is not a Swiss scenario nor Norwegian scenario. It's not even Andorrean scenario. It's a caravan of merchants scenario. It's how trade is done with Borat in some Kardashianstan.