Missed 16 invoices.

It depends on many factors (the amount, the correct vAT % for the product).

Kind regards, Kurt

21% vAT

Which product?

Just my product sales.

Do I have to redo my invoices or can I just edit them?

You will have to create credit notes for this, and then you must also send the credit note to your customers.

And then can I edit them?

You enter the change in the credit note. Never edit an invoice that has already been created.