When creating a new booking, to prevent the creation of duplicate customer entries, always search for the customer first.

The easiest way to do this is to always search for the customer post code as the first part of your completing a booking.

From the booking screen, enter the customer's postcode in the postcode field, and click the magnifying glass icon. A window will pop-up, if there is already a customer on the system with that postcode, as in this case, they will be show first.

If the customer is in the list, clicking the customer will attach that customer to the booking as below:-