Stripe has raised $70 million in a funding round which values the San Francisco-based payments start-up at $3.5 billion, according to the Financial Times.
The investment represents a doubling of Stripe's value since an $80 million round in January, and brings total funding to around $130 million for the firm, which only launched publicly in late 2011.
Founded by 20-something brothers Patrick and John Collison, Stripe provides merchants with an API that they can embed into their Web sites to easily accept credit card payments. It processes billions of dollars a year - taking a 2.9% cut of transactions and 30 cents - for thousands of firms.
The company has spent the last year scoring deals with some of the tech industries biggest players. It is behind both the Facebook and Twitter 'buy' buttons, has nabbed a deal with Chinese giant Alipay and been anointed a "highly recommended" partner for Apple Pay.