You can set the credit for a customer in the Business relationship tab in the the data of that same customer.
Once the credit is entered, when it saved the calculation for all of unpaid amounts of the open bookings and the invoices for that customer will be calculated.
If the sum of these amounts do not exceed the credit, the customer is not over the credit limit
If the sum is greater than the credit limit, the overexposure is shown in red on the right.
Every quotation and booking made for a customer over the limit shows the name of the customer in red.
In the same way, the name of this customer is also shown in red in the Agenda.