THE European Commission published a letter to the Irish government today, suggesting that tax rebates granted by Dublin to iPhone-maker Apple appeared to be illegal.

It said that Apple’s tax treatment raised “doubts about the compatibility” with EU law, which forbids government aid on free market grounds.

Apple funnels the bulk of its international sales through subsidiaries in Ireland, where it benefits from low, negotiated tax deals.

The commission complained that tax deals struck with Apple in 1991 and then 2007 showed “several inconsistencies” and may not have complied with international taxation standards.

The EU first announced the probe in June and it is requesting further documents from Ireland now before making a decision, which is likely to take several months.

If the preliminary finding by the EU competition commissioner is confirmed, Apple could face a repayment bill to the Irish government worth billions of dollars.