Corporate Income Tax: Effective Tax Rates Can Differ Significantly from the Statutory Rate

A letter report issued by the Government Accountability Office with an abstract that begins "Effective tax rates (ETR) differ from statutory tax rates in that they attempt to measure taxes paid as a proportion of economic income, while statutory rates indicate the amount of tax liability (before any credits) relative to taxable income, which is defined by tax law and reflects tax benefits and subsidies built into the law. Lacking access to detailed data from tax returns, most researchers have estimated ETRs based on data from financial statements. A common measure of tax liability used in past estimates has been the current tax expense--either federal only or worldwide (which comprises federal, foreign, and U.S. state and local income taxes). The most common measure of income for these estimates has been some variant of pretax net book income. GAO was able to compare book tax expenses to tax liabilities actually reported on corporate income tax returns.