There are no routine passport controls in operation for Irish and UK citizens travelling between the 2 countries. However, you must show identification to board a ferry or an airplane, and some airlines and sea carriers only accept a passport as valid identification.

As of February 25, 2026, travel requirements between England and Belfast have become stricter depending on your choice of airline. While Belfast is part of the UK and remains within the Common Travel Area (CTA)—which technically allows British and Irish citizens to travel without a passport on paper—airlines like Ryanair and Aer Lingus now mandate a valid passport or Irish Passport Card for all flights between Great Britain and the island of Ireland. This change was implemented to ensure "operational consistency" and security ahead of the UK's full Electronic Travel Authorisation (ETA) rollout. If you are flying with British Airways, they generally still accept other forms of government-issued photo ID (like a driving license) for domestic UK flights to Belfast, but they warn that many codeshare flights are operated by Aer Lingus and will require a passport. If you are traveling by ferry (e.g., from Liverpool or Cairnryan), you generally do not need a passport and can still use a valid driving license or similar photo ID. However, to avoid any risk of being denied boarding, carrying a passport is now the "de facto" recommendation for all travelers crossing the Irish Sea.