For the U.S., I doubt there are criminal laws to worry about in this case. You can always get sued for "fraud" (not-criminal), but who sues for $50?
About the only criminal area you need to worry about is mail fraud. Which would be fraud while using the U.S. postal service. But that's not a real concern either, as your only using mail to process refunds, not to solicit. You also don't need to use the mail, as you can require faxing or email of birth info. btw, IANAL.
