In 2026, while you can technically buy tickets at the station, pre-booking InterCity trains in Ireland is highly recommended. Irish Rail (Iarnród Éireann) offers significantly lower fares—often up to 50% cheaper—for those who book online at least a few days in advance. More importantly, popular routes like Dublin to Cork, Galway, or Belfast can sell out of seat reservations during peak times and weekends. If you have a "Free Travel Pass" or an Interrail pass, you should still use the "Reservation Only" option online for a small fee (typically €2.50) to guarantee a seat. For local "Commuter" or "DART" services around Dublin, pre-booking is not necessary; you can simply use a TFI Leap Card to tap on and off at the station gates for the best flexible rate.