I was planning on having a chat with my local bar owner about accepting Bitcoin. In putting together a little diagram on how it all works I found something that is lacking in request/payment system. That is tips for service.
In a credit card transaction a slip is presented to the customer that includes a place for adding a tip amount. While with credit cards the card is preauthorized an amount and then a tip can be added before final processing.
I know that tipping is primarily a U.S. custom, but it would be considered bad form to hand the bill back to a server and have them add a tip amount and bring you back a new bill.
A proper methodology would be to present a bill, possibly with a QR payment code already printed and in the customer wallet be able to have a line item for a service tip. This would fall in line with what people are already used to doing. The wallet application should allow the add on amount, but not allow the amount to be reduced prior to payment.
I would also suggest that the Bitcoin URI be expanded to include a tip field boolean to trigger that action in the wallet.
What do you guys think?