Irene, yes, unfortunately because people cheat and lie about shops. I had a scheduler tell me that some shoppers don't complete the shops at all, just take photos off the internet. So the receipt is "back up" proof, as is a Geoverify code, names and descriptions, and detailed timings, so the client can pull the security tapes and check on you.
I did a big box store last month, and got ONE question back from the scheduler/editor: Did you do this shop alone?
Well, of course I did. But I'm one of those people who are not very good at standing in line, and I DID chat with people in line with me. And sitting in my car, waiting to return my purchase, a couple came out of the store and I struck up a rather long conversation with them. They were parked beside me, in a car identical to mine (same make, model, year, color, etc. -- 20 year old Buicks!). We had a long chat about, of all things, our cars! We both have 300,000 miles on our cars. The couple, a man and a woman, were about my age, and had bought their car new. I explained all that in my reply to the scheduler. I'm sure it could very well have looked like I was with one of the people I chatted with in line.