Upside App -- No Receipt Required

Not sure if this would be the right community, but here's my question:
I recently got the Upside app, particularly to save on gas. The first time using it, it asks for a receipt. Not a shocker, but the gas pump doesn't print out a receipt.

My understanding is some locations don't require a receipt. My question is -- does this happen with certain companies (i.e., Racetrac), or is it more random than that? If it is based on certain companies, I'd like to know which ones.

I'm not saying I can't go into the gas station and ask for a receipt, but if I'm going to do this frequently, it certainly makes things more inconvenient.

Thanks