Apple is going into battle against an EU tax bill.
The U.S. tech giant on Monday (September 16) sends a six-person team to Europe's General Court in Luxembourg.
Their mission: to overturn an EU order that it pay 14.4 billion dollars to Ireland in back taxes.
Three years ago the European Commission ruled that Ireland's low tax-deal with Apple amounted to illegal state aid.
It pointed to a tax rate of just 0.005 percent paid by the firm's Irish unit in 2014.
Apple says it followed all laws to the letter, and it says it's fair to pay most of its taxes in the U.S., as that's where its products are designed and developed.
Dublin is on its side. The Irish government says its tax regime is key to attracting multinational firms, which employ about ten percent of its workforce.
European Competition Commissioner Margrethe Vestager doesn't buy it though.
She's also gone after so-called sweetheart deals offered by the Netherlands to Starbucks, and by Luxembourg to Amazon.