Thank you for contacting us, elsalty.

I'm glad to clarify this situation.

The Open Invoices report is sorted alphabetically by the name of the customer. And, the purpose of the Sort by button is to arrange the transactions in ascending or descending order depending on your needs.

I've attached screenshots below to show you how it works.

You can also refer to this article, Customize reports to learn more about the source and targets when filtering the data. It includes instructions and detailed steps for your guidance.

Feel free to leave a comment if you have follow-up questions. I'm always around to help you out.