I've been asked to give a talk at a Shanghai university (not being paid - it's sort of a good-will exchange between my university and this one). As it was relatively last minute I had to buy the ticket myself, with the understanding that they would reimburse me when I got there. I just found out that I'm going to be paid in CYN, which is a bit worrisome as I've read that you can only exchange currency back to dollars if you have a receipt that you exchanged the dollars to CYN to begin with. Is that true?

Looking forward to visiting Shanghai!