You would need to return to the place that issued the money order.I had to do that once, and the issuer had me write u201cnot used as intendedu201d somewhere on the money order.But don't write anything until they tell you to do so because the issuer may have a different policy than the place where I bought mine!They also had me write my name on the money order as the person who bought it, on a different line on the money order.The bottom line here is, you will most likely get the money back.But you may not get it back right away, because they may have a policy that requires you to wait until they can confirm it is in fact a money order they issued, and that varies from one company to another.Keeping that in mind, you may want to go during the week and during business hours even if the location is open late and on weekends because they may need to verify it by talking to someone at a different location in their main office which might be closed after hours and on weekends.