Apple and the Irish state are believed to be centering appeals against the European Commission's ruling that the company was given a sweetheart tax deal by arguing that the focus of the investigation changed without either party being notified.

The Irish Times cites "people with knowledge" of the cases who spoke under the condition of anonymity, they say that the probe into Apple's tax affairs moved away from an initial focus on transfer pricing.

This is when a corporation sets prices within its separate companies for goods and services, to effectively pay itself for its good and services. This can be used to move income into regions with lower tax rates.

Transfer pricing is referred to 26 times in the EU's 21 page document outlining the details of the Apple investigation in 2014 - but the actual ruling against Apple focused on the flow of income from around Europe into Apple's Irish vehicle which the EU said has no staff and no premises in Ireland or anywhere else.

Transfer pricing is never mentioned in the document issued with the Commission's findings.

The report says that this represented a shift in focus, which the Commission would have been required to inform Irish officials about.

It adds that both parties approached the Commission in late 2014 as word of a change in the investigation's focus began to circulate but neither party received "clear information" from the EU.

Following the ruling, Apple’s general counsel, Bruce Sewell said, "The Commission changed course a number of times and has taken all sorts of steps to obscure that fact from us and from the Irish."

"We were not given the opportunity to defend this case in the way that we should’ve been," he continued.

Commission spokesman Ricardo Cardoso has said that Apple and Ireland were kept up to date as the investigation unfolded - and that the core focus of the investigation never shifted.

Apple is also reported to be preparing another appeal relating to the investigation's operational procedures.