While Apple hasn’t been able to estimate the amount, it could be “material”, the California-based company said in a filing with the Securities and Exchange Commission.
It said in January that such an action could “adversely” affect its cashflows and financial condition.
The commission last year said it was looking into whether Ireland improperly gave Apple’s two subsidiaries state aid.
In September, the commission said Irish tax authorities failed to conform to international guidelines when they “reverse engineered” a deal with Apple to determine its bills. The findings were preliminary.
“The company believes the European Commission’s assertions are without merit,” Apple said in the filing.
If the commission concludes against Ireland, the country could be required “to recover from the company past taxes covering a period of up to 10 years” reflecting the disallowed state aid, Apple said.
The commission’s review can take more than a year, and decisions can be challenged at the European Court of Justice in Luxembourg.
The Department of Finance said that Apple “did not receive selective treatment and was taxed fully in accordance with the law”.