European Union competition regulators have today fined Facebook €110m for giving misleading information during a vetting of its deal to acquire messaging service WhatsApp in 2014.
The European Commission, which acts as the EU's competition watchdog, said it was a "proportionate and deterrent fine".
The Commission said Facebook had said it could not automatically match user accounts on its namesake platform and WhatsApp but two years later launched a service that did exactly that.
"The Commission has found that, contrary to Facebook's statements in the 2014 merger review process, the technical possibility of automatically matching Facebook and WhatsApp users' identities already existed in 2014, and that Facebook staff were aware of such a possibility," it stated.
Facebook said in a statement the errors made in its 2014 filings were not intentional and that the Commission had confirmed they had not affected the outcome of the merger review.
"Today's announcement brings this matter to a close," Facebook said.
The fine would not reverse the Commission's decision to clear the purchase of WhatsApp and was unrelated to separate investigations into data protection issues, it added.
The Commission could have fined Facebook up to 1% of its turnover - which would have been $276m based on 2016 results.
But it said that Facebook had co-operated with the proceedings and acknowledged its infringement.
The EU sanction comes after Facebook received a separate €150,000 fine earlier this week by a French data watchdog for failing to prevent its users' data being accessed by advertisers.
Last week the Italian competition authorities levied a €3m fine on WhatsApp for allegedly obliging users to agree to share their personal data with Facebook.
"Today's decision sends a clear signal to companies that they must comply with all aspects of EU merger rules, including the obligation to provide correct information," EU Competition Commissioner Margrethe Vestager said in a statement.
"The Commission must be able to take decisions about mergers' effects on competition in full knowledge of accurate facts," she added.