This was my manager rules and I don't think it was the fast food place rules.
I remember when I was working for a fast food place. If someone tried to pass a counterfeit bill, we would confiscate it. We would tell the customer that the bill was fake. (keep in mind that the customer knew). The customer would complain and want the bill back. However, when they made such a fuss we would tell them to go ahead and call the police. We would also say in fact if you like we can call them for you.
My first time they tried to pass a counterfeit bill, it was a 100 dollar bill. The bill was done very poorly. It didn't feel right. I also looked at it for a few minutes. I realized that it wasn't my glasses or my eyes at the time. It was fuzzy. The print was a horrible job.
I ended up grabbing my manager (I wasn't a manager at the time there). He looked at the bill and took over from there. I got a bunch of hi-fives that day, and then we put the bill up on the bulletin board in the back for everyone to see a counterfeit bill. That customer demanded that we give him back his "money". However we kept it since he didn't want the police involved and he left right away.
My manager went ahead and voided the order for me.