To see payments which were received but not yet applied to an invoice, you can use the Outstanding Pre-payments report.
You can find it by following the next steps:
1. Main Menu ->Reports -> Practice Analysis
2. In the Analysis Report section, choose the time period and location.
3. Then click Select report -> Financial Transactions -> Outstanding Pre-payments -> choose your preferred format:PDF or CSV. 
The PDF report will open in a separate tab and the CSV report will download to your desktop.