Seat reservations aren't included in your Interrail Pass – they're an additional supplement charged by some railway companies to make sure everyone gets a seat on busy services.

Seat reservations are often seen as expensive because they are an additional mandatory supplement charged by individual national railway companies, rather than the Interrail organization itself. High-speed and international trains, such as the Eurostar or TGV, require these fees to manage capacity and cover the costs of premium onboard services like high-speed Wi-Fi, power outlets, and air conditioning. In 2026, some international routes can cost between €30 and €45 per seat. These fees also act as a revenue stream for rail operators to maintain high-speed infrastructure. To avoid these costs, travelers can opt for regional or local trains, which rarely require reservations, though this often results in a significantly longer and more "scenic" journey with multiple transfers.