I've become religious about tracking paper receipts over the last year (and can't wait until all receipts are digital). That means I've tried most of the big-name iOS receipt scanner apps. Out of all of them, an app called Piikki (US$2.99, universal) is my favorite.
On the surface, Piikki is similar to other receipt scanner apps. It photographs receipts and saves the image to your phone. But the beauty of Piikki is in its tagging and archival power. Every time you photograph a receipt, the date, time and geolocation are saved. Users can then enter a title for each receipt, select a category the receipt falls into, select the appropriate currency and add tags.
Piikki can archive receipts in the app itself, or -- best of all -- it offers several export and sync options, including via Evernote, Dropbox and Google Drive. When browsing archived receipts on your iPhone, you can search via tags, names, locations, dates or more. Another great feature is the bar chart that displays receipt totals organized by category (such as "Travel" or "Food").
The app also offers a myriad number of settings, including passcode lock, image formats (JPEG or PDF), image quality, app themes and more. But my favorite part of Piikki is how it adds a small footer to the JPEG or PDF of the receipt. When I open a receipt on my computer (after it's been synced via Dropbox), not only do I see an image of the receipt, but the footer at the bottom shows me its name, location, date and time, category and tags.
Piikki is well worth the $2.99 price and I highly recommend it to individuals who like to track their paper receipts and small businesses as well. Best of all it's a universal app, so it works on the iPhone and iPad.