The European Court of Justice (CJEU) has ruled against Ireland in an appeal over state aid.
The case concerns a tax break given to the Aughinish Alumina facility in Co Limerick.
The state aid covered the period 2002-04 and concerned a tax exemption from excise duty for heavy mineral oil used to produce aluminium.
All Member States must apply for an exemption from excise taxes. Ireland had previously done this but ceased applying for exemption from 2001.
The Irish State was involved in lengthy litigation to try to stop the European Commission from making the Irish Government recover €10m which the EU said was illegal state aid.
Yesterday Ireland, along with Italy, lost a second appeal at the European Court of Justice over the cases that have been running for 14 years and featured five appeals.
The CJEU agreed with the Commission that Ireland and Italy provided illegal state aid from 2002 to 2004 through a tax exemption from excise duty for heavy mineral oil used to produce aluminium.
The origins of the case date to 2005 when the European Commission ruled that Aughinish Alumina had received €10m of illegal tax breaks and ordered repayment.
The Irish Government appealed the finding to the European General Court, which in 2007 overturned the Commission's order.
The European Commission then appealed the General Court's 2007 finding to the higher court, the CJEU.
It overturned the General Court's verdict and sent the case back to be reheard by the General Court.
The General Court pronounced the Commission decision null, and said the EU Council of Ministers had previously allowed excise exemptions.
The CJEU in 2013 again found the General Court was mistaken and sent the case back for examination.