While visiting Vienna, I noticed that receipts bear a QR-Code. This in itself is not unusual in Europe, they typically contain some link for online surveys or games. But here the data is not an URL, but the data of the receipt. It seems this was introduce this year to minimise cheating.
Poking a bit around, the QR-Code seems to contain the the identity of the seller, the date of the transaction, the total amount of the transaction, and some form of signature.
While looking around for more information, I realised there is also a project for a standard format on Swiss bills. The goal here is slightly different, as this is meant for processing of paper bills, there is also a European standard for doing this: EPC QR codes.
Having a machine readable version of the information present on bills and receipts is really a good idea. For bills, this means the information can be entered in the payement system with no transcription errors, for receipts, it makes things like expensing easier, when I travel I typically need to collect receipts, scan, them, and then tell the system which expense they pertain to.
While QR-Code is one possible carrier for the data, another one is to embed the machine readable data within the PDF file of the receipt, this is what the ZUGFeRD standard does, an EDI version of the bill is embedded in XML in the PDF.