Access a business partner and select the Business relationship tab.
If the business partner is a customer, you can see the total amount for the quotations, bookings and invoices made to that customer in the last twelve months, in addition to the amount of any unpaid bills.
Configure the default data to use when invoicing this business partner regarding Chargeable Tax, Payment Method, Bank and Deferred Days.
You can see an example in the following image.
If the business partner is a supplier, you can see the amount for the assigned bookings and invoices received from this business partner as a supplier, and the amount of the invoices unpaid. See an example below.
If it is both a customer and supplier, the previous part are both shown.
Click on the blue arrow to the left of any amount to open the corresponding list (bookings, quotations, or invoices) filtered to show only the rows responsible for that amount.