The European Union has launched a probe to determine whether the special tax deals offered to Apple and Starbucks by authorities in Ireland, Luxembourg and the Netherlands amount to illegal state aid.
"In the current context of tight public budgets, it is particularly important that large multinationals pay their fair share of taxes," EU Competition Commissioner Joaquin Almunia said on Wednesday.
Starbucks and a number of other multi-national companies - including Amazon, Google and Apple - have come under pressure from politicians and campaigners over their tax affairs.
The European Union said it would focus its probe on transfer pricing payments, an accounting technique where units of a multinational pay 'royalties' to another unit of their business.
The tax mechanism - made possible by carefully crafted tax laws in Ireland, Netherland and Luxembourg - allow operations in higher-taxed countries to post losses, with profits posted elsewhere.
Almunia said these arrangements could amount to illegal state aid that discriminated against other member states.
"Under the EU's state aid rules, national authorities cannot take measures allowing certain companies to pay less tax than they should if the tax rules of the Member State were applied in a fair and non-discriminatory way," Almunia said.
Last year, in the face of a public backlash over its tax arrangements in Britain, Starbucks agreed to pay STG20 million ($A36.51 million) in instalments of corporation tax, adding it had "listened" to its customers.
In 2012, Starbucks acknowledged it had not paid corporation tax in Britain on sales worth STG400 million between 2009 and 2012.
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