Hello, we offer holiday parties and invoice a deposit to hold the date. When the party is over we process the final payment. How would I open the invoice, update it with new items (like the drinks they bought that evening), then have the customer pay the remaining balance and be able to add a tip? So far I can only send them the invoice via e-mail with a tip option, or pay in person on a mobile device, but not be able to tip. Please help, we would love our tips this holiday season!
