Occasionally, just the same as the UK, a country issues a new note and withdraws the old one. The withdrawn currency is usually accepted for a while after the issue of the new currency to allow for a smooth transition to take place, but eventually, the old currency will cease to be legal tender. After that time, the old notes cannot usually be exchanged. If you're not sure whether the foreign money you have can still be exchanged, it is best to contact the supplier beforehand and they will gladly help you to determine whether your notes can be accepted.