Invoice was mistakingly duplicated. Can the Invoice be deleted or is there a specific process to follow?

Welcome to the Community page, @Dickens. I'd be happy to walk you through the steps on how to delete a duplicate invoice.

Here's how:

1. Go to Sales tab and select Invoices.
2. Find and open the duplicate invoice.
3. Click More actions at the bottom.
4. Select Delete and click Yes.

For your visual reference, I've attached some screenshots below:

Please check this article to learn more about voiding or deleting other transactions. 

You can always reach out to me if you need anything else about invoice or handling transactions. Have a great day!