The European Union is investigating Microsoft over the bundling of its chat and video app Teams with its Office product.

The U.S. tech giant has racked up 2.2 billion euros ($2.5 billion) in EU antitrust fines in the previous decade for practices that violate EU competition rules, including tying or bundling two or more products.

The EU’s investigation followed a complaint by Salesforce-owned workspace messaging app Slack in 2020 and after Microsoft’s attempts to resolve the issue did not address the EU competition enforcer's concerns.

The EU said in a statement it has formally opened an investigation to assess whether Microsoft has breached EU competition rules by tying or bundling its communication and collaboration product Teams to its popular suites for businesses, Office 365 and Microsoft 365.

The commission wants to fast-track the case and will likely issue formal charges against Microsoft this fall unless the company improves its concessions.

"We respect the European Commission’s work on this case and take our own responsibilities very seriously," a Microsoft spokesperson said in a statement to FOX Business. "We will continue to cooperate with the commission and remain committed to finding solutions that will address its concerns."

The EU competition enforcer said it was concerned Microsoft may be abusing and defending its market position in productivity software by restricting competition in the European communication and collaboration products market.

"Remote communication and collaboration tools like Teams have become indispensable for many businesses in Europe," EU antitrust chief Margrethe Vestager said in a statement. "We must therefore ensure that the markets for these products remain competitive and companies are free to choose the products that best meet their needs."

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Shares of Microsoft are up about 39% year to date.

Reuters contributed to this report.