Currently there is provision to add a customer on the fly in the POS modal. Details Here: http://feedback.repairshopr.com/forums/165658-general/suggestions/10893585-pos-add-customer

We rarely use this as it creates poor quality data, we like to capture the referral source for every customer. So I would like to suggest you can customize the customer fields to be added on the fly in the POS Module.

Other users may wish to capture more info on the fly like addresses. The big one for us is referral source.