With $181.1 billion offshore, Apple tops the list of U.S. companies that keep their profits abroad. Overall, 72 percent of Fortune 500 companies keep $2.1 trillion overseas, according to data gathered from public filings by Citizens for Tax Justice.

To put it in perspective, Apple’s cash hoard outside the country far outstrips the combined overseas profits of Microsoft and Google, $108.3 billion and $47.4 billion respectively. Here’s a look at the top 15 U.S. companies that keep portions of their profits abroad:

If Apple were to bring its profits back to the U.S., it would owe $59.2 billion extra in taxes alone, according to the study. And since its profits overseas go to its Irish subsidiary, it pays a much lower income tax rate of about 2.3 percent.

Microsoft employs similar tactics overseas through its subsidiaries in Ireland, Luxembourg and Singapore. As a result, it paid a tax of 3.1 percent on its $108.3 billion in profit. But the money didn’t go too far. According to a 2013 report from the Wall Street Journal, 93 percent of Microsoft’s foreign profits were invested in U.S. government bonds, corporate bonds and mortgage securities. The company would owe $34.5 billion in U.S. taxes if it were to bring its overseas profits home. That same year, Google’s Irish subsidiary paid an effective tax rate of 0.16 percent on $22.8 billion in revenue, according to Ars Technica.

The party is expected to end soon for some companies, however. European Union member states agreed Tuesday on the automatic exchange of information on cross-border tax rulings.

“The automatic exchange of information on tax rulings will enable member states to detect certain abusive tax practices by companies and take the necessary action in response,” the European Commission announced in a press statement. “It is expected that this initiative will deter tax authorities from offering selective tax treatment to companies once this is open to scrutiny by their peers. This will result in much healthier tax competition.”

EU member states will have to pass those rules into law before the end of 2016, which then come into effect on Jan. 1, 2017.