Apple and the Irish government outlined their grounds to challenge an EC decision to make the company pay €13 billion plus interest in back taxes to the country, ahead of an Apple appeal this week.

The company’s CFO Luca Maestri and General Counsel Bruce Sewell told Reuters Apple’s argument centres on claims the EC disregarded advice from Irish tax experts and deliberately “exploited loopholes” to maximise the fine.

The Irish government is also attempting to get the judgement reversed. In its submission, published earlier today, it accuses the Commission of “exceeding its powers” and “misunderstanding the relevant facts and Irish law”.

Ireland’s Department of Finance (DoF) submitted a detailed breakdown of its views to the European Courts in November. Among the claims, the DoF stated Apple had simply applied the long-standing Irish law around the taxation of profits directly attributable to the office rather than non-Irish profits.

In August, Apple was ordered by the EC to pay €13 billion plus interest to Ireland in unpaid taxes. It ruled Apple was allowed to pay lower rates of tax compared to other businesses operating out of the country between the years of 2003 and 2014 which, the EC stated, is illegal under EU law.

EU competition commissioner Margrethe Vestager, explained the decision, stating: “This selective treatment allowed Apple to pay an effective corporate tax rate of 1 per cent on its European profits in 2003 down to 0.005 per cent in 2014.”

Apple immediately stated its intent to appeal the judgement, and in November the Irish Department of Finance (DoF) lodged its own Annulment Application with the General Court of the EU.

Ahead of the appeal, the EC today publicly revealed the full ruling on the August case, reiterating its belief that Apple had paid “substantially less tax than other businesses”.