On 1 December 2020 Salesforce announced it would buy Slack Technologies, the workplace messaging company, for about $27.7 billion in cash and stock. It was the largest acquisition in Salesforce's history. The deal did not close until 21 July 2021. The seven-month gap prompted questions about whether it would go through at all.
The deal had been agreed, not completed
The merger agreement was signed when the deal was announced. What remained were the conditions to closing: approval by Slack's shareholders and clearance from competition regulators. Large deals in the US must be notified to the Federal Trade Commission and the Department of Justice under the Hart-Scott-Rodino Act, and cannot close until a waiting period ends.
The antitrust review
The Justice Department sent a "second request" for more information, which extends the review while regulators examine whether a deal would reduce competition. Slack competed with Microsoft Teams, and had filed a competition complaint against Microsoft with the European Commission in 2020, so the market for workplace collaboration tools was already under scrutiny. Salesforce and Slack said they expected the deal to close once the review concluded.
Slack shareholders approved the deal in March 2021. In July 2021 Salesforce announced that the waiting period had expired and the acquisition closed shortly afterwards. No court challenge was brought.
What happened next
Slack became part of Salesforce and was integrated into its products. Its co-founder and chief executive, Stewart Butterfield, stepped down at the start of 2023. The European Commission's investigation into Microsoft's bundling of Teams, prompted partly by Slack's complaint, continued; in 2025 the Commission accepted commitments from Microsoft to offer its software suites without Teams.
Why it matters
The episode is a good example of the difference between signing and closing a deal. Announcements create the impression that a transaction is done; in law, many large deals spend months waiting for regulators. Antitrust review of technology deals has become more intensive since 2020 on both sides of the Atlantic.
Sources
General information about the law as it stood when this page was updated, not financial, tax or legal advice. Rules and limits change; check the official source or a qualified adviser before acting.