The European Commission ruled on Monday that a corporate tax break that Belgium has granted to at least 35 companies, amounting to total reductions equivalent to about $765 million, was illegal.
The commission, the executive arm of the European Union, did not immediately identify the companies that benefited from the tax break.
The commission said the Belgian government would be required to recover the unpaid taxes from the companies.
The ruling, part of a series of investigations led by the European Union’s competition commissioner, Margrethe Vestager, found that Belgium had given unfair tax advantages to certain companies — ones that were not available to other companies doing business in Belgium.