When a customer is traveling between different countries, he is eligible to buy goods without tax. However, on the same trip there might also be customers who are only travelling domestic. An idea would be to let the QR-code on their ticket decide whether the transaction should go to a customer with or without sales tax. A standard solution for this would add great value for airports/cruises. How the customer should be tagged as tax-free/domestic based on the values in the QR-code would have to be configured on the back-end.