San Francisco-based workplace collaboration platform Slack has soared in market value to  $7.1 billion (£5.4); up $2 billion in less than a year, following a $427 million (£331) Series H funding round announced today.

The company raised $250 million from investors in a funding round led by Softbank last September that valued the company, on paper, at just over $5 billion.

Slack said at the time of that round that it has “yet to spend much of our existing capital,” and is hoping for “operational flexibility”.

The lead investors in this Series H equity round were General Atlantic and Dragoneer Investment Group. The company’s rapid growth is continuing and Slack — which now has eight million daily active users — said it sees scope do more, faster.

Slack said in a blog post: “We pursued this additional investment to give us even more resources and flexibility to better serve our customers, evolve our business, and take advantage of the massive opportunity in front of us.”

“Our mission is to make people’s working lives simpler, more pleasant, and more productive, and we are grateful for the support along the way.”

Three Million Paid Users; $7 Billion Slack Valuation… 

Slack launched four years ago and has reported this year that they have over eight million daily active users (DAU) using the service across more than 500,000 organisations. Of this number, some three million are paid users.

While it is free to create a team messaging group on Slack, this only comes with basic support and 5 GB of storage total.

The next tier is billed at £6.30 per active user per month. This comes with heightened security measures, more intelligence in the search options and 10 GB per team member. A premium service of £11.70 is also available.

One of the investors in this round of funding for Slack is T. Rowe Price Associates.

Alan Tu, Equity Research Analyst with the firm commented in an emailed statement that: “Slack has made strong progress in a very short time in this new era of enterprise collaboration.”

“Our investment represents our belief in the company’s vision and leadership team, together with the product’s potential to increase productivity and change the way people work on an even larger scale.”

Over half of Slack’s users are now outside of the US “Italy is our fastest-growing market outside the US for paid users, Austria for newly paid teams, and Japan just surpassed the UK to be our second-biggest market by DAUs.”

See also: Slack arrives on Linux with a snap