Taxation is one of the significant phenomenons in any economy as its not only generates revenue for existing government but serve as a fiscal tool as well as stabilization policy. One of the main types of taxation is the petroleum tax which accounts for more than 30% of revenue for developed countries and more than 85% for developing economies. This work focuses on comparative analysis of three petroleum producing giants: Nigeria, United States of America and Iran. The tax system have changed over time with changing circumstance: the structure of political environment, the nature of respective oil industry, the policies of the individual oil associations belonged to, the price of oil and domestic demand. The study found amongst other that the tax systems of the three countries are fixed over time and the not adequately flexible to attune to profitability or non-profitability of oil as well as price.