When you book an international ticket for ICE to/through Germany, the supplement is included in the price of your ticket. Book your international ICE ticket at:
Do you want to travel comfortably within the Netherlands on the Amsterdam Centraal - Utrecht Centraal - Arnhem Centraal route? Then you will have to pay a supplement in addition to your domestic ticket, both in 1st and 2nd class. Buy this supplement in advance on NS.nl, at the NS ticket machines or a NS Service desk. The price is € 3 for a single journey.
If you have a NS season ticket you can travel on ICE within the Netherlands without having to pay the supplement.