Which countries do not have an income tax requirement?

As many as nine countries in the Americas region don't have an income tax requirement, a study by Voronoi showed. These include Cayman Islands, Bermuda and The Bahamas. Middle-East countries including UAE, Qatar, Oman, Kuwait and Bahrain also don't charge income tax. Citizens of Asian countries North Korea and Brunei along with Europe's Monaco and Vatican City too are exempted.