Good day, @wchdds,
Let's pull up the Open Invoices report to show the customers running balance. This report shows all unpaid invoices and statement charges including the totals for each customer.
Feel free to read through this article: Customize your reports in QuickBooks Online. This link will help you filter reports to show specific accounts or customers just the way you want them.
Once your customers pay what their invoices, you can then record their payments. Check this out for the detailed steps and additional information: Record a customer payment.
Keep me posted if there's anything else you need and I'd be glad to help.