When can the amount charged temporarily exceed the real amount?

On certain trains, metro trains and streetcars, you can pay for your ticket directly with your Nickel card. 

In this case, the information we receive does not allow us to know the final price of your ticket. For this reason, we may initially charge an additional €5 (estimated ticket price + €5). If this happens, the adjustment will be made within a few days (1 to 3 working days depending on the case) and you will be reimbursed if you have been charged more than the actual price of your ticket. 

No action is required on your part.

Please note that this does not apply to payments at ticket counters or in-station vending machines. This only concerns payments on machines located inside the means of transport.

This may be the case on the Keolis and RATP networks in France, the Renfe network in Spain, EMT in Valencia, De Lijn and STIB in Belgium, for example.