Irish Passport card is a travel document that Irish citizens can use for certain travel instead of the standard passport book. It is similar in size to a credit card. You can use the irish passport card when traveling in the European Union, the European Economic Area (which includes Iceland, Liechtenstein and Norway) and Switzerland. You do not need a passport to enter the United Kingdom, but airlines and sea carriers may want you to prove your identity when checking in. You should check with your airline or sea carrier to see what types of identification they accept.