The paper examines the country’s top 500 non-individual taxpayers for taxable years 2009-2011. It also analyzes the profile of the top taxpayers as well as their effective tax rates (ETR) and identifies the top corporations which are consistently included in the Business World (BW) ranking of top corporations but not listed among the BIR’s 500 top taxpayers. The top 500 corporate taxpayers in 2011 were engaged in various activities, majority (25%) of which belong to the manufacturing industry, followed by wholesale and retail trade, 15%; financial and insurance activities, 14%; real estate activities, 11%; and electricity, gas and water, 7%. The remaining top taxpayers were engaged in transportation and storage, information and communication and administrative support activities, among others. A more or less similar distribution of top taxpayers, by industry is observed in 2009 and 2010. In terms of income tax paid, the top 500 corporate taxpayers paid a total income tax amounting to PhP144.5 billion in 2011 which accounted for 43% of the corporate income tax (CIT) collection of the BIR during the year. Of the amount paid in 2011, the top taxpayers in manufacturing sector contributed 28%; electricity, gas and water, 15%; information and communication, 13%; real estate activities, 8%; mining, 7%; wholesale and retail trade, 7%; financial and insurance activities, 6%; and other industries, 16%. The same industries contributed the bulk of the income tax collections in 2009-2010. On the other hand, the Top 10 corporate taxpayers paid a total income tax amounting to PhP53.98 billion in 2011, up from over PhP40 billion in 2009 and 2010. Their income tax payments in 2011 accounted for 37% of the total income tax paid by the Top 500 Corporate Taxpayers or 16% of the total CIT collection during the same period. The ETR or ratio of income tax paid to gross revenue in 2011 of the Top 10 Corporate Taxpayers are as follows: Shell Phils Exploration, 25%; Chevron Malampaya LLC, 24%; Smart Communications, Inc., 12%; SM Prime Holdings, Inc., 11%; Petron, 1%; MERALCO, 3%; San Miguel Brewery, Inc. and Globe Telecom, Inc., 8%; and PMFTC, Inc., 5%. These imply that while some top taxpayers contributed as much as a quarter of their gross sales receipts as income tax in 2011, others shared only 1-3%. It may be worth mentioning that corporations registered with the country’s Investment Promotion Agencies (IPAs), specifically the Board of Investments (BOI) and the Philippine Economic Zone Authority (PEZA) may have low ETRs due to the fact that they enjoyed ITH and/or were subject to the 5% special tax on gross income in lieu of national and local taxes. Also, a comparison of ETRs among top corporations engaged in similar activities shows that the ETRs varied and each taxpayer registered erratic ETR year by year. Therefore, it is recommended that top revenue grosser with very low ETRs and corporations engaged in the same line of business with incomparable ETRs be flagged for audit by the BIR.