Eight of the 100 highest earning Irish-based multi-nationals are paying no corporation tax whatsoever, five have a tax bill of less than 1% and others are effectively being paid by the taxman because of serious loopholes in the tax system.
The State's financial watchdog revealed the shocking situation at the start of a detailed Dáil meeting with Revenue this morning despite Revenue chairman Niall Cody insisting: "I don't believe Ireland is a tax haven."
The Public Accounts Committee also heard concerns raised over delays in receiving the €13.1bn Apple tax and fears US president Donald Trump may "repatriate" firms in Ireland before the money is handed over.
In his opening overview statement during the cross-party committee meeting, Comptroller and Auditor General Seamus McCarthy said despite repeated public criticism over the Government's approach to multi-national firms, some of the largest are paying nothing in taxes to Ireland.
Of even more concern, he said some of the largest firms involved are in reality being given money by the taxman instead of paying money into the Exchequer.
"Eight of the 100 companies with the highest taxable income had effective tax rates of zero, including some which had negative rates - ie, instead of corporation tax, they received rebates. A further five had an effective rate of less than 1%.
"These very low effective rates reflected the use by the companies of significant tax credits and reliefs in particular double taxation relief and research and development tax credits," Mr McCarthy added.
While the Comptroller and Auditor General also said it needs to be noted that two thirds of the highest earning companies also pay a de facto tax rate of 12%, or more, the zero tax rate, 1% rate and payment to companies is likely to lead to significant criticism over Ireland's tax laws.
At a later discussion in the meeting, Revenue chairman Niall Cody - who initially told the PAC the effective overall corporation tax rate for 2015 was 9.8% - rejected claims from Sinn Féin TD David Cullinane Ireland is a tax haven.
"I don't believe Ireland is a tax haven," he said.
The PAC meeting also heard concerns raised by PAC chair and Fianna Fáil TD Sean Fleming and Fine Gael TD Alan Farrell over delays in Apple transferring the €13.1bn Apple tax to the State's escrow account.
Department of Finance assistant secretary general John Hogan told the committee this is likely to occur early next year, but did not directly address concerns raised over US president Donald Trump's overnight comments about foreign-based US firms and fears he may seek to "repatriate" the money before it is transferred.
Ireland's tax situation has come under intense scrutiny in recent years from other EU member states, with Taoiseach Leo Varadkar and French president Emmanuel Macron clashing over the issue at a meeting last month, amid disputed claims Ireland's laws mean we are effectively a tax haven.