Since the enactment of the Transport (Re-organisation of Córas Iompair Éireann) Act, 1986, CIÉ has been the holding company for Bus Éireann, Dublin Bus and Iarnród Éireann/Irish Rail, the three largest internal transport companies in Ireland.

It was originally to have operated the Luas tram system in Dublin, but that project was transferred to the newly created Railway Procurement Agency (RPA).

It owns all fixed assets used by the three companies, such as railway lines and stations, the latter being dealt with through the Group Property division.

[3] The Transport Act 1950 amalgamated CIÉ and the Grand Canal Company and formally nationalised CIÉ, changing its structure from that of a private limited company to a corporation under a board appointed by the Minister for Transport.

[citation needed] For most of its existence, CIÉ, in particular its railways division, made large losses and was subsidised by the taxpayer.

In a similar pattern to that seen in many other states, Ireland's railways were accordingly rationalised, and suffered severe cutbacks while at the same time the road division was expanded.

[citation needed] The Baker Tilly report found an amount of corporate malpractice in 2004–08.