Overview
This only applies if you generate your invoices in Music Monitor. If you export your billing information for use in another system, this does not apply.
There is an option in Music Monitor to include the outstanding balance on invoices. It shows the sum of all billing lines on the account. If selected, it shows as an additional line after the total of the current invoice.
Setup
Go to Common Tasks > Set up - Conservatoriums > Set up invoice template
In the bottom right part of the setup screen is an option to Display total outstanding balance (including previous invoices) on each invoice?
Simply select Yes to this.
Invoices will now show the balance of the current invoice, but also another line stating the total outstanding across all of this customer's invoices.
Note: Although the text says "previous invoices", in fact it counts all invoices as well as line items that have not yet been invoiced. If you have this enabled, and you open an old invoice, you will see the current account balance including more recent invoices.