According to Forbes, Robinhood, which offers a free trading service, confirmed a new funding round on Thursday that quadruples its valuation to $5.6 billion and makes it one of the most richly-valued startups in the country.

The San Francisco-based brokerage said it has raised $363 million in a Series D round led by DST Global, the investment firm started by Russian billionaire investor Yuri Milner. Other investors in the round included Sequoia Capital, Capital G (formerly Google Capital), Kleiner Perkins and ICONIQ.

Robinhood plans to put the funds toward launching additional free financial services offerings and beefing up its customer service and engineering teams.

The company was started in 2013 by Stanford graduates Vlad Tenev and Baiju Bhatt, who wanted to bring down the cost of trading and allow more Americans to participate in the financial markets. Whereas brokerages like E*Trade and TD Ameritrade charge $6.95 for every trade, Robinhood is completely commission-free.

The service attracted more than 4 million users, who can take positions in individual stocks, as well as mutual funds, ETFs, options and cryptocurrencies. Since inception, the company says that users have carried out $150 billion in transactions and saved more than $1 billion in fees.

"This is a moment along our journey to take stock of the work we've done and then quickly move on and continue to do stuff," says Bhatt, 33, who shares CEO duties with Tenev. "We are continuing to launch new products that lower the barriers of entry and make things more cost-efficient."

In February, Robinhood began rolling out a service for users to trade bitcoin and other cryptocurrencies for free. It is currently available to users in ten states. In doing so, Robinhood is taking on exchanges that specialize in digital money and charge a fee for all trades, such as Coinbase, a cryptocurrency trading platform backed by Andreessen Horowitz, the New York Stock Exchange and others.

Robinhood has continued to offer its main service at no cost to users in part by keeping its own expenses low. It doesn't have storefront locations, has done little marketing and employs just 200 people. The company primarily makes money through its premium offering, called Robinhood Gold, which charges users a flat fee for additional features like after-hours trading and the ability to buy stocks on margin. Bhatt declined to say how many users pay for a premium membership or whether the company is profitable.

Robinhood is now the second most highly valued financial technology startup in the country behind Stripe, which allows merchants to accept online and mobile payments and is valued at $9.1 billion. Robinhood's total amount of funding stands at $539 million. It was previously valued at $1.3 billion after raising $110 million in a 2017 funding round also led by DST Global.

The funding round was first reported by The Wall Street Journal in March.