The European Union’s crackdown on corporate tax avoidance has landed on Apple; the Union’s antitrust regulator is demanding that the United States tech giant pay Ireland up to 13 billion euros ($14.5 billion) plus interest in back taxes.

The ruling is the highest-profile move yet in the European battle to make international companies pay what authorities consider their fair share of EU taxes. The EU charges that Apple and other big companies struck deals with EU countries to pay unusually low tax in exchange for basing their European operations there.

The US government has countered that European officials are unfairly targeting American companies.

Following are some questions and answers about the issue.

Q. Why did the EU launch the tax crackdown?
A. European countries are keen to attract big companies to their territory; sometimes too keen, with some offering ultra-low tax rates as incentives. So the EU launched a drive to combat tax avoidance by investigating the deals that allow multinationals to slash their bills in countries like Luxembourg, Ireland, and the Netherlands. The EU says some 50-70 billion euros ($56-79 billion) are lost every year due to tax avoidance. Also, some multinationals shift their earnings made in EU countries to the one low-tax country they are based in.

Q. Don’t EU countries have their own tax laws?
A. They do. The European Commission says it’s not interfering with members’ rights to set their corporate tax rates, but that it should help protect countries from unfair tax competition. When one country’s tax policy hurts a neighbor’s revenues, that country should be able to protect its tax base.

Q. Why does the US government care?
A. The US Treasury Department released a report last week claiming that American companies were being unfairly targeted in the probe and that doing so could end up costing American taxpayers. That’s because businesses get US tax credits for their foreign tax payments. Apple and other US firms leave much of their foreign earnings overseas to avoid higher US tax rates. Treasury officials say they’re working to get companies to repatriate those funds.

Q. Can Apple afford to pay the judgment?
A. Easily, given that the company’s cash hoard exceeds $200 billion. At the end of June , Apple reported holding $231.5 billion in cash, cash equivalents and marketable securities. The company held $214.9 billion of that amount in foreign subsidiaries.