If there is a vat difference on the imported purchase, it lets you amend the number in the vat field, but then the total doesn't update on screen even if tab through. Eg. I have an invoice, £15.82 + VAT. Automation thinks it should be £3.16 VAT but on the invoice it is £3.17. I amend as such, but it shows £15.82 + £3.17 = £18.98