“Tax rulings that artificially reduce a company's tax burden are not in line with EU state-aid rules. They are illegal,” said Margrethe Vestager, the EU competition commissioner. “I hope that, with today's decisions, this message will be heard by member state governments and companies alike. All companies, big or small, multinational or not, should pay their fair share of tax.”

The Dutch and Luxembourg tax authorities must work out the actual amounts to be recouped based on a method provided by the European Commission. The recovery orders may also have an impact across the Atlantic, where tax credits can in theory be granted when multinationals repatriate earnings from subsidiaries, according to a U.S. Treasury Department official.

Tax Repayment May Be Extremely Expensive

Still, “any amount repaid will not automatically qualify for credit against the group's U.S. tax bill—it will be a complex question depending on the company's particular circumstances,” said Heather Self, a tax partner at law firm Pinsent Masons LLP.

Luxembourg disagrees with the EU commission's conclusions and “will use appropriate due diligence to analyze the decision of the commission as well as its legal rationale,” the country's finance ministry said in a statement.

The country, which still faces an ongoing EU probe into a tax ruling set up with Amazon in 2003, said the regulator's criteria in finding state aid in these accords were “unprecedented” and that it “has not established in any way” a selective advantage to the Fiat unit.

The Dutch government said it “is somewhat surprised about the decision” that Starbucks received state aid. The EU's conclusion “raises a lot of questions and requires careful consideration. The Netherlands is convinced that actual international standards are applied and shall, therefore, analyze the commission's criticism carefully before taking a decision on further steps.”

Starbucks said it “shares the concerns expressed by the Netherlands government that there are significant errors in the decision, and we plan to appeal since we followed the Dutch and OECD rules available to anyone.” Starbucks said it paid $3 billion in global taxes between 2008 and 2014.

The Organization for Economic Cooperation and Development (OECD), a research institute funded by 34 countries including the U.S., sets tax standards used by countries across the world. The OECD is seeking to curb tax-haven use and other fiscal strategies by companies.

Fiat “did not receive any state aid” and “any finding in this matter would be immaterial to the FCA Group's reported results,” the company said in an emailed statement on Tuesday. A Fiat spokesman in Turin said Wednesday that the company had no further comment on the issue.

Apple May Owe a 'Material' Amount

Apple raised a flag in April about the potential cost if the company is required to pay past taxes to Ireland as part of the commission investigation. While Apple hasn't been able to estimate the amount, it could be “material,” the Cupertino, California-based technology company said in a filing with the U.S. Securities and Exchange Commission (SEC).

Vestager said regulators are still poring over cases involving Amazon, Apple, and the system of fiscal rulings in Belgium. They are all different and will each be assessed on their merits, Vestager told journalists in Brussels Wednesday. Additional cases may also be in the pipeline, she said.

“We do not stop here. We continue the inquiries into tax rulings in all EU members states,” Vestager said at a press conference. “In terms of timing” of the open probes, “fast is always better than slow, but best of all is to be just,” and the EU will make a decision “when a case is ready.” Amazon and Apple declined to comment.

The estimated amounts the two companies will have to pay back to Luxembourg and the Netherlands “are not spectacular sums, but basically that's not the message here; the message here is the principle,” Vestager said. Also, the amounts are “much, much more than what has previously been paid.”

Some May Use Intercompany Transactions to Evade European Taxes

The EU repayment order isn't enough to force big companies to pay their share, according to a group campaigning for fairer taxation.

“It's obviously still worth the risk to try and avoid taxes, when the worst that can happen is that a few of them get caught and have to pay their taxes, while the rest of them can continue enjoying a free ride,” said Tove Ryding, coordinator of tax justice at the European Network on Debt and Development.

In the Starbucks case, the commission said a Dutch unit paid millions of euros to a U.K.-based arm of the company that isn't taxed in Britain in exchange for a technique to roast coffee beans. Exaggerated tax-deductible royalty payments for this technique allowed Seattle-based Starbucks to unfairly lower its Dutch taxes.

Starbucks said the commission “wrongly asserts that independent third parties which roast coffee beans for Starbucks do not pay equivalent royalties as our own roasting plant in Amsterdam. This is false.”

In the Fiat case, the commission said a unit in Luxembourg benefited from a selective advantage since 2012 when it was given a tax ruling. As a result of the special arrangement, the unit ended up paying only “a small portion of its actual accounting capital at a very low remuneration,” and if estimations had been in line to market conditions, “the taxable profits declared in Luxembourg would have been 20 times higher,” Vestager said.

The Brussels-based commission is bracing itself for legal challenges and spent months honing its arguments so they stand up in court.

Many companies had similar tax arrangements, and the EU courts will end up ruling on them, said Falk Schoening, a competition lawyer and expert on state aid law at Hogan Lovells in Munich, Germany. “This may just be the beginning.”

–With assistance from David de Jong in Amsterdam, Dara Doyle and Joe Brennan in Dublin, and Tommaso Ebhardt in Milan.

Copyright 2018 Bloomberg. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.