The iPhone maker is appealing to Europe’s second highest court to overturn the European Commission’s 2016 ruling that it pay the record sum to Ireland. Ireland who believes its economy has benefited from investment by multinational companies attracted by low tax rates, is also challenging the Commission’s decision.

Apple accused the Commission of using its powers to combat state aid “to retrofit changes to national law”, in effect trying to change the international tax system and in the process creating legal uncertainty for businesses.

The EU executive dismissed the arguments, saying it was not seeking to police international tax laws and accused Ireland of not having done its homework when assessing Apple’s taxes.

Apple’s arguments at the General Court, Europe’s second-highest, came after the EU executive in 2016 said the tech giant benefited from illegal state aid due to two Irish tax rulings which artificially reduced its tax burden for over two decades.

Apple’s Chief Financial Officer Luca Maestri led a six-strong delegation to the court where a panel of five judges will hear arguments over two days.

Apple’s lawyer Daniel Beard told the court that the Commission contends that essentially all of Apple’s profits from all of its sales outside the Americas must be attributed to two branches in Ireland.

He said the fact the iPhone, the iPad, the App Store, other Apple products and services and key intellectual property rights were developed in the United States, and not in Ireland, showed the flaws in the Commission’s case.

“The branches’ activities did not involve creating, developing or managing those rights. Based on the facts of this case, the primary line defies reality and common sense,” Beard said.

“The activities of these two branches in Ireland simply could not be responsible for generating almost all of Apple’s profits outside the Americas.”

Beard dismissed criticism of the 0.005 per cent tax rate paid by Apple’s main Irish unit in 2014, which was cited by the Commission in its decision, saying the regulator was just seeking “headlines by quoting tiny numbers”.

Paying an average global tax rate of 26%, Apple has said it is the largest taxpayer worldwide and is now paying around 20 billion euros in US taxes on the same profits that the Commission said should have been taxed in Ireland.

In its current financial quarter, Apple expects revenue of $61-64 billion and a gross margin of 37.5-38.5%.

However Commission lawyer Richard Lyal said Apple’s argument that all its intellectual property-related activities take place in the United States was pants.

He said the EU was interested in taxing Apple’s Irish subsidiaries, not the group nor Apple worldwide.

 Ireland had failed to examine the functions performed by Apple’s Irish units, the risks assumed and the assets used by the subsidiaries.

“They simply accepted an arbitrary method proposed by the Apple Ireland subsidiaries. That in itself gives rise to a presumption of a special deal, exceptionally advantageous treatment. It is clear that the tax authorities made no assessment in 1991.”

Luxembourg, told by the EU to recover millions of euros in back taxes from Amazon, Engie and Fiat, is backing Ireland. Poland and the EFTA (European Free Trade Association) Surveillance Authority support the Commission.

The court is expected to rule in the coming months, with the losing party likely to appeal to the EU Court of Justice and a final judgment could take several years.