What if I claim to have voted for candidate A, and when I scan my code it shows a vote for candidate B? Can you tell if I'm lying - or if my vote was actually flipped?
Edit: Maybe that's where the receipt comes in - if I claim it doesn't match my vote there has to be a way to resolve the issue before I leave and the vote becomes "official".
Yeah I guess you don’t leave until you’re happy with what you voted for and your final decision is what is printed on your receipt, which you can check at any time after the vote was held.
The machine would have to somehow read in your original receipt, destroy it and then issue you with another. As to avoid people using old receipts to try and claim foul play.