Hi, 

I’m planning on buying an interrail mobile pass. My passport has expired and I will not be able to get a new one until June. My questions is: is it possible to buy a mobile pass with the expired passport number and change the passport number on the interrail pass later on? I would likt to buy the interrail pass now rather than later since there is a discount now and I also need the interail pass number to be able to make seat reservations.