Stripe is gaining more financial allies to help it take on the digital payments industry.

The start-up, based in San Francisco, said on Tuesday that it had raised new funding from investors like Visa, American Express and Sequoia Capital, among others, valuing the young company at $5 billion. That is a significant jump for Stripe, coming roughly six months after it garnered $70 million at a $3.5 billion valuation. Stripe declined to disclose the amount of new funding, except to say it was “less than $100 million.”

Founded five years ago, Stripe has quickly gained traction by offering simple software and services for online small and medium-size businesses. Similar to Square and PayPal, Stripe accepts credit and debit cards for merchants who have not taken them previously. Stripe charges a small fee per transaction.

On Tuesday Stripe also announced a partnership with Visa, one of the world’s largest credit card companies, in which the two will work on ways to improve digital transactions. The companies said they expected to collaborate on initiatives like payments security, as well as software like website “buy buttons.”

Stripe said it would rely on Visa’s global footprint to expand its international availability. Stripe is currently available to businesses in more than 25 countries, and hopes to expand further with help from Visa.