How borders are drawn and enforced has far-reaching consequences, whether we live on either side of them or halfway across the world.

Apple’s tax payments around the world have come into the spotlight again this week after the American tech giant was hit with a €13 billion ($14.5 billion) tax penalty by the European Union. The European Commission said that Apple’s special tax arrangements with Ireland amount to illegal state aid, and the Irish must now recoup the funds. Under the deal, Apple used various shell companies to pay an effective tax rate on its European profits of 1% or less between 2003 and 2014, the commission said.

Apple holds more assets offshore than any of its American counterparts, which reduces its tax bill there, its biggest market. But it is still paying more in the US than anywhere else—the company set aside $16.1 billion for US federal and state taxes in its latest fiscal year (pdf, p.55), and just $2.9 billion for foreign taxes.

China has long been a crucial growth engine for Apple, although its saturated smartphone market has made things tougher of late. Greater China (including Hong Kong and Taiwan) is Apple’s third-biggest regional market behind the Americas and Europe—and for much of 2015 was its second-biggest market.

So what does Apple pay in taxes in China? The opaqueness of Apple’s tax disclosures, coupled with the opaqueness of China’s government disclosures, makes figuring that out difficult. An Apple spokesperson in Hong Kong did not respond to emailed questions about taxes in China.

Judging just from the information available, it still seems remarkably low.

China’s corporate tax rate is 25%, falling between the US’s 35% and Ireland’s 12.5% rates. The Chinese government can lower the rate to 15% for industries it wants to encourage, which includes technology, a category that may very well apply to Apple.

The company earned $23 billion in operating income in Greater China in its latest fiscal year, so by a completely crude measure, even if all of the $2.9 billion it set aside for foreign taxes for that period were paid in China and none elsewhere, it would still be paying less than a 15% tax rate—about 12.6% to be exact. Much of that $2.9 billion is probably being paid to the EU, its second-biggest market, meaning China’s tax collectors are getting even less.

The company’s practice of holding its intellectual property rights in Ireland probably lowers its Chinese tax bill, as it does for other tax bills around the world, Robert Willens, a tax consultant and Columbia Business School professor of taxation, explained on CNBC this week:

When an Apple iPhone is sold in China, for example, Apple’s Chinese subsidiary must pay the Irish company to reflect the use of the Irish companies’ intellectual property. Only Apple knows what percentage of that iPhone sale is subject to those intellectual property licensing fees… But the result is that profit earned on the sale in China is shifted to the Irish subsidiary.

China’s State Administration for Industry & Commerce doesn’t require China-registered corporate entities to publish their financial statements, so there’s no public channel to investigate Apple’s Chinese tax liabilities, said Chen Zongshan, a tax lawyer at DeBund Law Offices in Shanghai.

In order to reduce its taxes, Apple is “likely” to move earnings out of China by trading with its subsidiaries in lower-tax states, a common strategy employed by multinationals, Chen noted. China’s regulations addressing these sorts of maneuvers “started relatively late” because the government didn’t want to “harm foreign investors’ enthusiasm,” Chen added.

The company’s tax practices in China, like just about everywhere else, have come under scrutiny. In September last year, China’s finance ministry said Apple underpaid taxes in 2013 by $71 million. Apple’s Shanghai unit failed to account for $1.4 billion in sales in 2013, according to the ministry. Apple claimed it was a result of the company’s misinterpretation of Chinese tax rules, and paid $80 million in back taxes and fines.