The only way I see this or the mobile payment technology apple is supposed to release taking off is if they are combined. Don't have your iPhone or don't want to pull it out of your pocket/purse? Just use your finger for Touch ID on your watch and then tap it to pay. If you don't want to buy an I watch, no problem - you can use your phone.
Either way, the receipt can be found at any time using the built in purchase app on your iPhone or iCloud.com account.
Either way, the receipt can be found at any time using the built in purchase app on your iPhone or iCloud.com account.