Thanks for getting back to us, @mkkc.

I'm happy to know that the steps provided by my colleague helped you set up a default invoice template.

To delete the test invoices, here's how:

1. Go to the Sales menu at the left pane, then Customers.
2. Select the name of the customer you've created the test invoices with.
3. On the Transaction List tab, click to open the invoices one at a time.

4. Choose More at the bottom, then Delete.

That should do it. For additional information, check out this article: How to void or delete an invoice or other transactions.

Let me know how it goes or if you need anything else in the comment. I'm always here to help. Take care and enjoy the rest of the day.