Corporate Income Tax, Effective Tax Rates (EFT) Can Differ Significantly from the Statutory Rate, GAO-13-520, May 30, 2013: “For tax year 2010 (the most recent information available), profitable U.S. corporations that filed a Schedule M-3 paid U.S. federal income taxes amounting to about 13 percent of the pretax worldwide income that they reported in their financial statements (for those entities included in their tax returns). When foreign and state and local income taxes are included, the ETR for profitable filers increases to around 17 percent. The inclusion of unprofitable firms, which pay little if any tax, also raises the ETRs because the losses of unprofitable corporations greatly reduce the denominator of the measures. Even with the inclusion of unprofitable filers, which increased the average worldwide ETR to 22.7 percent, all of the ETRs were well below the top statutory tax rate of 35 percent. GAO could only estimate average ETRs with the data available and could not determine the variation in rates across corporations. The limited available data from Schedules M-3, along with prior GAO work relating to corporate taxpayers, suggest that ETRs are likely to vary considerably across corporations.”