For domestic travel within the Netherlands in 2026, you do not need to buy tickets in advance. The Dutch national rail (NS) operates on a "walk-on" basis where prices are fixed by distance; there is no discount for booking a week early, and you cannot reserve seats on standard Intercity or Sprinter trains. You can simply "tap-and-go" with your contactless debit/credit card or mobile phone at the station gates (OV-pay), which is the most convenient method. However, for international travel (e.g., to Paris, London, or Berlin), buying in advance is highly recommended and often essential. High-speed trains like the Eurostar, ICE, and Nightjet use dynamic pricing similar to airlines, meaning a ticket booked three months early could be €40, while a last-minute ticket could exceed €200. These international trains also often require a mandatory seat reservation, which can sell out during peak 2026 travel seasons. For local Dutch trips, just show up and tap; for crossing borders, book as soon as your dates are confirmed.