A simple way to cut back on paper receipts is to have the proof of purchases sent to your email account. To organize your digital receipts, use an app to keep them categorized and accessible. OneReceipt is a free app that can store not only your receipts, but your credit card and bank statements, too. If you happen to get a paper receipt, you can just take a snapshot with your phone and OneReceipt will add it to your digital collection. The app is available for iPhones only.