...an employee you're pretty sure you caught stealing?

Here's the skinny. In June of last year, I did a Five Guys shop and paid cash. Got my receipt home, uploaded...BOOM, email from QC. "Why does this say employee discount?" My reply: "...huh? Why DOES it say employee--I don't know. I didn't notice before I left the store. I definitely paid $11.44 for my order, not $0." They checked the camera: I was telling the truth. So probably employee error, I got paid, all happy. Shopped him again a few months later with card, no problem. Shopped him a third time with cash...and guess what I saw on my receipt?

Unfortunately, that was my first FG shop after the guidelines were changed in January and I hadn't corrected my order when it was wrong, so the shop was rejected and the information about the receipts didn't go to the client. This shop is one of my regulars and sooner or later odds are good I'll see him again--and after I was greeted by name in a different FG near the theatre I work at, I stopped using my card for shops so there's no name to make my face more memorable, which means next time I'll be paying cash again.

I still haven't tossed the "problem" receipt from June 2013 and there's a digital copy on my computer. If I get this guy a third time and this happens, what should I do? I have a hard time believing a manager makes this error routinely but only on cash orders.

I always check the receipt to make sure it's correct with the price and food order.

I would continue to report just as you have reported the previous incidents. It is not up to the shopper to make judgements or to determine what is happening and why. It is the shopper's job to objectively report what happened. Be sure to look at your receipt to be sure it is correct. If your receipt is not correct, note in your report that the receipt you were given is not correct and explain what is not correct. Let the client connect the dots after you describe what happened.

Could also not be the employee's fault. Could be
they are being told to do that on cash orders so
the franchise owner can avoid paying taxes or royalty fees
on their sales....

I think this would just be something to look out for next time, and if it happens again, I would lay out the facts as you saw them. Assuming the report does not offer a narrative block where this infor would logically go, I would draft an email to the scheduler/help desk. As a MS'er, I don't think it would be worth the likely hassles in going outside the IC agreement to contact the company. I know some may differ, in that recurring theft might be worth letting the company know--even if you lose that shop in the future (or possibly all shops with that MSC).

I would just take the extra reporting step to the MSC and let them do with it what they will.

No, if I reported it'd be through the help desk, which has always lived up to its name for me at this company (including walking me through their site on a day when a "routine maintenance" update shattered the code). I'm just wondering if it's something I should comment on. It's not an avoiding taxes thing--I've had my order taken, with cash, by two other people there and not had this happen.

I think you should definitely comment on the receipt being incorrect.

I shopped a parking lot once. We drove in past a huge sign that said "Flat Rate $5". Pull up to the booth and the guy says "Seven dollars". I tell him the sign says five and he's like "OK, five dollars". Didn't even attempt a story like "it's evening rate now" or something. I assume he was pocketing the extra $2. I put exactly what happened in the report and never heard about it again.