American corporations paid an average tax rate of eight percent on their company profits in Ireland, according to a report compiled for American politicians.
The document, released to RTE News under Freedom of Information, shows the companies were paying less than the normal corporation tax rate of 12.5 percent.
Companies can do this by claiming tax credits for different purposes, including research and development.
In one year, U.S. companies paid €1.29 billion to the Irish Revenue Commissioners and repatriated €16.1 billion to the U.S.
The figures were based on an analysis of 304 tax returns by companies examined by the Congressional Budget Office in a report published in January of this year.
They are based on the most up-to-date figures available which relate to 2008.
The document, called Options for Taxing US Multinational Corporations, outlines a number of alternatives for ensuring the companies pay more tax.
When the companies repatriate money to the U.S. they still have to pay tax, although the U.S. authorities adjust the bill to take account of payments made to the Irish Revenue Commissioners.
However, the companies can also pay low tax in Ireland and defer sending the profits back home.
The report shows despite the fact that Ireland is a relatively small economy among developed nations, it was the fourth largest source of repatriated income to the U.S. in 2008.
Five percent of the total income of U.S. companies who repatriate profits came from Ireland, according to the report.
It says U.S. corporations which paid tax abroad have reduced their income tax liability by about 40 percent.
The document says the current U.S. tax code "encourages firms to artificially shift reported income abroad and between foreign countries."
The report highlights tax rates in 34 developed countries and finds that Ireland has the lowest corporation tax rate at 12.5 percent. The average rate among the other 34 countries is 19.1 percent.