Void sale before batch sends out
must have the option to void the sale before the batch send out on the end of the day. very important.
David Eberting commented
You can void (refund/exchange does the same thing as a void (Customer will not see it on their statement as long as it's done before the batch) a sale if you have the right permissions. Go to Orders. Click on the order and look for the appropriate button on the right.
You can refund a single item but if you need to also add an item you would have to either charge that item individually or rebuild the order.
If you took payment on the wrong ticket you can refund the whole ticket, go back into the order in the orders app, and it will now let you take a new payment for that order. But again you would have to rebuild the order if there need to be changes to the items.