Apple has been accused of using Ireland as a way of avoiding billions of euro in tax.
A US senate report said the iPhone set up companies in Ireland which paid little or no tax on sales of the company's products outside America.
The 40 page report said that Apple agreed tax at a rate of just 2% with the Irish government - well below the corporation tax rate of 12.5%.
Apple executives will be grilled by US politicians later on today on how much tax the company pays.
In a statement the company said that it does not use tax gimmicks.
Apple employs 4,000 people at its European headquarters in Cork.