Let me share some information to avoid getting duplicate invoices.
To start with, we haven’t received reports similar to this from other users. It’s possible that you've accidentally recreated the invoice while making some adjustments.
If the invoice is showing duplicate invoice numbers with accurate information, you can change manually change its invoice number. However, if it is indeed a duplicate invoice, you have the options of voiding or deleting it. One advantage of voiding a transaction is that there's a record of it, while the amount is zeroed out. Additionally, a voided transaction can be restored, while a deleted transaction is completely removed. Here's how to void and delete transactions:
Open the transaction you'd like to void or delete.
Select More at the bottom of the screen.
Choose Void or Delete.
Click Yes to confirm that you'd like to void or delete the transaction.
The following is a brief video to serve as a visual reference: