Always remember that VAT is due unless you can prove it isn’t. Proving that goods have left the UK is an absolute rule that should never be overlooked. If you can’t prove it then VAT is due to HMRC. It’s all about having the right bits of paper.
The tribunal decision in Grange Road Car Sales (TC05681) makes for interesting reading. This involved cars sold from Northern Ireland and driven away into the Irish Republic. The record of the taxpayer’s evidence is almost entertaining. Suffice to say the tribunal wasn’t convinced and the appeal failed.
The list of required evidence before VAT isn’t due on non-UK sales is quite long (in Notice 725) and has the power of law. In other words these evidence lists are not suggestions but requirements. The list is even longer if you don’t arrange the shipment, like with ex-works or drive away sales. If you don’t meet the requirements HMRC can and will treat the sale as including VAT and there goes a lot or even all of the profit.