How do I know the overall sales and revenue made in this financial year?

You can view the Sales by Customer report and the Payments Received report to know about the overall sales and revenue that you’ve made in the financial year. 

To access the report: 

• Go to the Reports module in the left sidebar.
• Click Sales by Customer under Sales or Payments Received under Payment Received section to view these reports. 
• Click the This Month dropdown in the top bar and select a date range (say, This Year) to run the report for that specific period. 

These reports will help you to know the overall sales and revenue for the financial year.