The EU could open an antitrust investigation into Microsoft’s video and messaging platform Teams, stemming from a complaint made by Slack back in July 2020, according to a report by Reuters.

Enterprise messaging application Slack, which has since been bought by Salesforce, originally filed a competition complaint against Microsoft citing “illegal and anti-competitive practice of abusing its market dominance to extinguish competition in breach of European Union competition law.”

The complaint further alleged that Microsoft has “illegally tied its Teams product into its market-dominant Office productivity suite, force installing it for millions, blocking its removal, and hiding the true cost to enterprise customers.”

Microsoft had seemingly been hoping to address the concerns with the EU before a formal investigation was opened, with Reuters reporting in December 2022 that the tech giant had made a “preliminary offer of concessions” to try and settle the European Commission’s concerns.

However, Reuters is now reporting that attempts by Microsoft to remedy the situation have hit a roadblock, specifically that the price reduction Microsoft offered for Office minus the Teams app was not as low as the EU had been hoping. Consequently, an investigation is now likely to take place and if found in breach of the EU’s antitrust rules, Microsoft risks being fined up to 10% of its global turnover.

Microsoft has faced a number of sanctions from the European Commission during the last decade, having been fined hundreds of millions of dollars by the Commission in 2004, 2008, and 2015.

Earlier this year the company attempted to ward off another potential investigation by reportedly agreeing to change its cloud computing practices in order to avoid an antitrust probe from the EU.

That potential investigation stemmed from complaints made by European cloud companies that raised concerns after their customers were asked to pay more to run Microsoft software in non-Microsoft cloud environments, under what they saw as restrictive cloud licensing policies.

In a statment, the EU Commission said it had received several complaints regarding Microsoft, including one by Slack about Microsoft’s conduct in relation to its Teams product, which it was assessing based on its standard procedures.

Microsoft did not immediately respond to a request for comment.