Hi there, tsmarble. You can go to the Customers tab and tap the specific customer you're looking for to see their outstanding balance.
It's shown on their profile page. You can refer to this visual guide below.

However, if you need a detailed breakdown, you'll need to log in to QuickBooks via your web browser and generate a Customer Balance Summary or Customer Balance Detail report to have a snapshot of what every customer owes.
Please let me know if you have more questions.