I have the same problem as the person who asked the question. I accidentally accepted a bank transaction that was already counted and included in the filed VAT return. This is because the VAT return has been created and filed from the manually uploaded bank statements. But my client, unknowingly, connected direct feed for the same bank and lots of transactions got duplicated and I had to cancel them, accepting only those that happened in the new VAT quarter. Accidentally, one transaction was accepted which belongs to the previous (already filed VAT quarter - flat rate). So, I do need to cancel this transaction not to double tax this income. What is the best way to do that please?