Business Insider reported https://www.businessinsider.com/ibm-slack-partnership-customer-digital-transformation-2020-2?r=US&IR=T earlier in the day that IBM would deploy the app to every single one of its 350,000 employees, making it the largest single customer for Slack, which has had a partnership with IBM since at least 2016.

"IBM has been Slack's largest customer for several years and has expanded its usage of Slack over that time," the company said in a regulatory filing https://www.sec.gov/Archives/edgar/data/1764925/000176492520000131/a8-kxitem701.htm, undercutting the idea that it had reached a major deal with IBM.

Shares of Slack, which soared 15% on the report, fell by over 7% in trading after the bell.

(Reporting by Ayanti Bera in Bengaluru; Editing by Vinay Dwivedi)