This is not something that is easy to do just by linking tables together and setting hide or suppress formulas on the report.
Do you need to include the data from paid invoices in any of the calculations on the report? If not, there is a way to do this using a Command (SQL Select statement)
instead of linking tables together.
If you'll go to the Database menu for the report, select "Show SQL Query", and paste the query here, I can rewrite it for you to show you how to do this.
Also, see my blog post for more info about how to properly use a Command in a report:
Best Practices When Using Commands with Crystal Reports
-Dell