The investment catapults the six-year-old start-up into the ranks of the unicorns, a popular term for privately held companies that are valued at more than $1 billion. Thumbtack was valued at around $750 million last year. The Scottish money management firm Baillie Gifford led the latest funding, which nearly doubles the amount of money Thumbtack has raised, and previous investors including Tiger Global, Google Capital and Sequoia Capital also participated.

'We're at the stage where we need to think about having a permanent capital base,' said Marco Zappacosta, Thumbtack's co-founder and chief executive. The new investment is what is known as a late-stage financing; the start-up previously raised five other funding rounds.

Baillie Gifford, a global money management firm with about $173 billion in assets under management, typically invests in companies, usually publicly traded, for the long haul. 'The venture investors do have to exit sometime and we want to invite in additional, long-term stakeholders that can support the sort of big, independent business we want to build,' said Mr. Zappacosta.

Thumbtack was part of a list recently created by the research firm CB Insights of 50 companies that might next hit the billion-dollar valuation mark. Before Thumbtack revealed its latest funding round, CB Insights said that three other companies from the list had hit that threshhold.

Bryan Schreier, an investor at Sequoia who worked on the Thumbtack investment, said that the start-up is looking at an unusually large investment opportunity because it 'is already delivering more than [$1 billion worth of business] to independent professionals, yet they're still only scratching the surface of the $500 billion plus local services market.'

Thumbtack essentially connects service providers with customers through its online marketplace. Under the company's business model, Thumbtack markets services on behalf of, say, a plumber, and then collects interested customers. The plumber pays a fee to contact the customers and send them quotes. Once that connection is made, the customers and professionals don't have to use Thumbtack again to maintain the relationship.

Thumbtack has 200,000 active professionals on the platform, 10 times more than in 2013. The company doesn't disclose revenue and is unprofitable.

Thumbtack said it plans to use the latest funding to build invoice, payment, scheduling and customer management services for small business owners.


'We want to make customer retention tools for professionals and give them reason to keep Thumbtack in the loop as they find and retain customers,' said Mr. Zappacosta.