No one knew what the new rules would be until the 24th of December. Yes companies probably should have prepared a suite of options they could switch to. But there was always the chance, and probably the reality that whatever they prepared would be wrong.
The case I've heard regarding british exports to EU involved something that could be relatively easy to get, as it was known that UK would be out of common VAT and customs union at the time, and is mostly related to personnel mistakenly continuing to issue invoices "business as usual".
Now, the import VAT situation is totally bonkers, and I'm really dismayed about how it's apparently going to hit us in EU too in June (media didn't give a peep about that one)
