How to change the invoice number

In order to change a given invoice's number, we first need to edit the invoice. This can be found in the drop-down menu next to the Email option, and is only available if the invoice does not yet have any payments logged against it:

When editing the invoice, you'll be able to change the number in the invoice number field, located near the top-right:

When you are finished, just clicking Verify & Finalize at the bottom right of the page and this will lock in the change.