Slack Discloses $141 Million Loss as Messaging Start-Up Joins Tech Listing Rush

SAN FRANCISCO — Slack, the workplace messaging start-up, disclosed the details of its business in an offering prospectus on Friday as it joined the parade of tech companies that plan to publicly list their shares this year.

Sharing its financial results widely for the first time, Slack said that it collected $400.6 million in revenue in its latest fiscal year, which ended Jan. 31. That was nearly double what it generated in the previous fiscal year. It lost $140.7 million in the latest fiscal year, narrowing its losses from $180.9 million the year before.

The company had 88,000 paying customers at the end of the most recent fiscal year, up almost 50 percent compared with the previous year. Of those customers, 575 paid more than $100,000 for their subscriptions, contributing about 40 percent of the company’s revenue.

Slack’s filing followed the initial public offerings of two other high-profile start-ups, Lyft and Pinterest. The biggest tech public offering of recent years — that of the ride-hailing giant Uber — is also on deck, with Uber pricing its shares on Friday in a stock sale that is expected to value it at as much as $91 billion.

Slack plans to list on the New York Stock Exchange under the ticker symbol “SK.”