In official documents published this morning, it says the Revenue Commissioners agreed special tax deals with the computer company in 1991 and 2007.
It claims that Ireland didn't change its usual corporate tax rate, but instead negotiated with Apple to decide how much of its profits would be taxed within this country.
Apple may be forced to pay decades of tax in arrears if it's deemed to have received unfair state aid from the Irish government
Ireland has always denied striking any special tax deals with multinational firms.
Suzanne Lynch, European Correspondent with the Irish Times, says today's document forms the basis for the Commission's full investigation into Apple's tax affairs, which could take years.
