Apple's 13bn-euro (around R219bn at current rates) battle with the European Union reaches the bloc's courts next month in a hearing set to throw the spotlight on antitrust commissioner Margrethe Vestager's crackdown on tax deals doled out to big companies.

The EU's General Court, its second-highest tribunal, will hear arguments in the challenges by the iPhone maker and Ireland over two days set for September 17-18. The US last year lost a bid to intervene in the case in support of Apple.

The European Commission in August 2016 ordered Ireland to recoup the record sum plus interest, saying the world's richest company was handed an unfair advantage. The EU decision reverberated across the Atlantic, triggering criticism from the US Treasury that the EU was making itself a "supra-national tax authority" that could threaten global tax reform efforts.

The Irish government said in an email it "profoundly disagrees" with the EU's decision and "is engaging fully with the process and ensuring the best presentation of the state's position".

Apple and the commission in Brussels didn't immediately respond to requests for comment.

Appeals over tax cases have been piling up at the EU's courts since 2015, when the commission issued its first orders against Luxembourg and the Netherlands to recoup unpaid taxes from a Fiat Chrysler Automobiles NV unit and Starbucks Corp. respectively.

The court heard arguments in both cases last year with rulings yet to come. A first ruling in the series of decisions by EU antitrust chief Vestager ended in a setback in February for the EU when Belgium won a bid to overturn an order to recoup about 800m euros from 35 companies, including Anheuser-Busch InBev NV.