How do I edit a published invoice?
If you’ve sent an invoice and it’s the latest in the invoice series, you can unpublish it. The invoice will then go back to "Drafts". Now you can make the changes you want before marking it as complete again and sending it to the customer.
If you use the accrual (invoice) method and you recorded the business transaction when you sent the invoice, you must cancel this journal entry before you can make any changes. Once you have done this you can click on "Edit" as shown below.
If the invoice is not the last to have been created, which means there are subsequent invoices with higher numbers, you can't undo publication. However, you can go in and make changes to update the invoice. Don’t forget to resend the invoice if you want the customer to take note of the changes.