The popular multinational ridesharing company Uber is in trouble again, and this time, it is thanks to state, federal, and foreign tax authorities. Uber’s large and complex structure makes their tax filings even more so. Uber is currently under audit by the IRS for tax years 2013 and 2014, but they are also under audit by multiple state and foreign tax authorities for returns going all the way back to 2010. Surprisingly, the issue in question isn’t the employment status of their drivers or their compensation policies, but rather the company’s transfer pricing positions.

Generally, transfer pricing refers to the method used to price transactions between related parties. For instance, like those between two companies who are subsidiaries or otherwise a part of the same multinational organization and that exchange goods or services with each other. But whenever two related companies trade with each other, there is an opportunity to artificially distort the price of their trade to minimize the resulting tax bill. For that reason, transfer pricing has become one of the most important issues in international taxation.

Transfer pricing and the associated allocation of income and expenses between members of the same multinational organization are critical procedures. Since the established price will directly affect the allocation of taxable income across all the companies that participate in the transaction, and as a result across several jurisdictions, the result of an audit will have an impact on several jurisdictions and several years. For instance, in Uber’s case, we see that it’s tax returns from 2010 through 2019 tax years are still open in several countries—the U.S., Brazil, Netherlands, Mexico, United Kingdom, Australia, Singapore, and India. In addition, the audit may result in additional tax liability over and beyond what has already been paid, the need to adjust the company’s financial statements, and may generate disputes over potential adjustments to income ranging from millions to tens of millions.

Uber’s case is a good example of a transfer pricing dispute that may last a while, but Uber is not alone. Amazon, AOL, Adobe, and Microsoft have made headlines for transfer pricing issues as well. And as in those cases, it may be a while before all of Uber’s tax issues reach a resolution. Most IRS audits take a long time to complete, especially on organizations as big as Uber, and foreign tax audits are unlikely to be completed quickly either.