Peer-to-peer money sending firm TransferWise has become profitable this calendar year, six years after being founded.
Its customers are now transferring more than £1bn every month, and it has 700 staff, it says.
TransferWise was founded by friends Taavet Hinrikus and Kristo Kaarmannhas who wanted to shake up the money transfer market.
It is valued at $1.1bn (£850m) and says it has more than one million customers.
The valuation makes it what is known in the trade as a 'unicorn' - a term used for firms that are privately-owned start-ups valued at $1bn or higher.
Mr Hinrikus said: "We're building one of the few new global financial services brands that are coming out now... To have hit break-even just six years on from launch shows how strong the foundations of our business are. This is just the starting point."
The firm made a loss before tax of £17.4m in the year ended March 2016, but says it was profitable this calendar year.
TransferWise has investors including Sir Richard Branson, Facebook investor Peter Thiel, Betfair co-founder David Yu, and venture capital firm Andreessen Horowitz.
The two Estonians started TransferWise in 2011 in London.
Mr Kaarmann had bills to pay in Estonia and his salary was in pounds, while Mr Hinrikus needed sterling to live in the UK but was being paid in euros.
They found a way of transferring money into each other's account without paying banks extra fees.