Ireland has provided the European Commission with details of Revenue tax opinions provided to more than 300 companies, including all opinions issued in the years 2010, 2011, and 2012.
The confirmation was made by the Minister for Finance, Michael Noonan, in response to a parliamentary question from Fianna Fáil's Finance Spokesperson Michael McGrath.
The opinions where handed over after a request from the Commission as part of its state aid investigations in different EU member states.
Mr McGrath said it is concerning that the Commission is examining the Revenue opinions "in light of the European Commission's investigation into the application of corporation tax to Apple".
He added: "This may well be entirely routine and it has to be said there isn't any suggestion that the Commission is about to commence a formal investigation in any of these cases.
"On a wider level, it is vital for Ireland to retain the certainty around our corporation tax rate and system, and that the integrity of Revenue opinions is upheld."
Mr Noonan also said Revenue has itself begun reviewing a number of opinions that were provided more than five years ago.