The top corporate income tax level in the United States is 35 percent. In the United Kingdom, it's 28 percent. But in Ireland, it's only 12.5 percent, and in Bermuda there's no corporate income tax at all. That means multinational companies that shift their earnings through Ireland or Bermuda can save billions of dollars in taxes each year.
http://www.npr.org/2011/03/17/134619750/how-offshore-tax-havens-save-companies-billions
