When a paid invoice has been included on a submitted VAT return, however, there is a mistake with the details or the invoice has been duplicated, you can make a correction by reversing this invoice and recreating a new invoice if necessary.
This guide explains the reverse process for paid invoices if you are on a cash accounting VAT scheme. You can check which type of scheme you are on within the Settings > Organisation > Details&Tax > Manage VAT schemes menu.
Head to Sales > Invoices and click on the Paid tab.
Click on the invoice number that needs reversing.
To create the reversal invoice, hit the Copy button.
Update the unit price so that the amount is changed to a negative value and then hit the Save button at the top of the invoice form.
Allocate payment using the 'Record payment' form. This paid invoice will have the effect of reversing the original in your accounts.
Once the invoice has been reversed a new copy of an invoice can be created with the corrections and payments made as necessary.
Please note: Both the reverse invoice and the corrected invoice will need to be included in a future VAT return.