Which country inside the United Kingdom does NOT appear on its flag, the Union Jack?

Wales does not appear on the flag of the United Kingdom, known as the Union Jack, because it was already annexed by England when the flag was created. The Union Jack is a combination of the flags of England and Scotland, representing the political union between these two countries. Wales, having been politically united with England since the 16th century, does not have a separate flag incorporated into the Union Jack.