• Guillaume Pousaz went seven years without accepting external funding for his start-up. Now, Checkout.com is one of the most valuable fintech unicorns in the world.
• The company has achieved impressive growth, increasing transaction volumes by 250% over the last year and picking up big-name clients like Klarna and Singaporean ride-hailing app Grab.
• Pousaz says Checkout is only scratching the surface, despite tripling its valuation last year to $15 billion, becoming Europe's most valuable private company.

Guillaume Pousaz went seven years without accepting external funding for his start-up. Now, Checkout.com is one of the most valuable fintech unicorns in the world.

Pousaz initially wanted to become an investment banker, but he dropped out of his college in Switzerland to become a surfer in California. The Swiss-born entrepreneur then found a job at International Payments Consultants, but left to try his luck at building a start-up. Pousaz eventually started Checkout.com in 2012 to solve the problem of online payment processing for merchants and their customers.

The company ranked No. 13 on this year's CNBC Disruptor 50 list.

Checkout.com mostly flew under the radar until 2019, when it tapped external investors for the first time to raise a $230 million Series A round. That deal — reportedly agreed over "handshakes" rather than term sheets — gave the firm the coveted status of "unicorn," with a $2 billion valuation.

Since then, the company has achieved impressive growth, increasing transaction volumes by 250% over the last year and picking up big-name clients — from Singaporean ride-hailing app Grab to Swedish fintech firm Klarna — along the way.

CNBC recently spoke with Pousaz, who says Checkout is only scratching the surface, despite tripling its valuation last year to become Europe's most valuable private company.

The following Q&A has been edited for length and clarity.

CNBC: It's been reported that you wanted to become an investment banker, but instead dropped out of college to become a surfer in California prior to starting Checkout.com.

Pousaz: I was drawn to financial services because of my interest in the way it powers and grows the broader global economy, but I was at a point where I was very curious and adventurous. That led me to California. I was excited by the creative, technology-first Californian mindset (as well as the surfing!). This is where I had my first exposure to the world of payments. I immediately saw the potential and issues that existed with many of the legacy providers. I knew there had to be a better way of doing things on a global scale.

Even in those early days, the e-commerce market was growing at 20% year over year. I believed digital commerce and payments would be the key to unlocking the next phase of global economic growth. Since launching Checkout.com in 2012, we've seen businesses embrace technology and the perception of payments shift from a commodity service to competitive advantage and a strategic growth lever.

Ultimately, I left California and started Checkout.com in the U.K., but our early Californian roots are reflected in our obsession with developer-friendly, best-in-class technology. Our global approach, rigor in developing the best technology, and the discipline we have had in building a sustainable, profitable business have defined Checkout.com since the beginning. Today, we have a global-but-local mindset. We believe in the importance of localization in our offering and the need to be on the ground to understand local nuances and consumer preferences to help us serve enterprises who have a similar global footprint and outlook.

CNBC: Your company is taking on fintech in a different way, thinking not just about a payments, but also payouts. How has the approach both benefitted and challenged you in such a crowded space?

Pousaz: We built Checkout.com to reinvent digital payments by delivering better performance and simplifying the challenges of scaling globally. That is still our core, but we have also evolved to create a differentiated offering for our merchants. Our technology is built modularly, empowering businesses with a tailored solution developed for their specific needs. We don't believe in a one-size-fits-all approach to payments; with Checkout.com our merchants only buy the products and features they need. Second, our deeply localized approach to building products means that we allow global businesses to meet the ever-changing needs of their customers, wherever they are in the world.

Specifically on payouts, we've uncovered an opportunity to empower merchants to optimize not only the way that money moves into their business — through payments — but also how it moves across and out of their business — through payouts, FX and treasury management, and, soon, issuing. That is incredibly powerful because it allows for innovation in digital commerce, such as marketplaces, the gig economy, and financial technology. We're partnering with merchants like Klarna, Farfetch, Revolut, and Wise to help them deliver more for their customers. We are just scratching the surface of what is possible with payout capabilities, and consumers are beginning to experience the benefit of this innovation.

CNBC: As a digital payments company, how are you thinking about the rise of certain cryptocurrencies? In the near future, do you anticipate accepting cryptocurrency as a form of payment?

Pousaz: We are really excited to observe the innovation happening in crypto right now. We are technologists at heart and believe in the power of tech to simplify financial services. At the moment, we work with crypto merchants like Coinbase to facilitate fiat to crypto on-ramps or payouts.

From time to time, we do hear from our merchants that they are considering accepting crypto payments. At the moment adoption remains relatively low, and so it has yet to make it onto our roadmap, although I think it's definitely possible in the future. We continue to be engaged in the conversation and developments of cryptocurrencies and believe in the need for strong regulation to protect the ecosystem and the consumers it serves.

CNBC: You've said before that the long-term goal is for a stock market listing, and more specifically that, "there's no alternative at this point, given the size of the business." Is there any particular route to the public markets that you find most interesting – namely via SPAC, direct listing, or the traditional IPO?

Pousaz: I do think that eventually a listing will be the right path for Checkout.com. Since the early days we have been profitable, which allows our team to continue delivering innovative product developments to serve as the backbone for the evolving digital economy. It also has allowed us to make strategic investments, such as Tamara and Thunes, to support the growth of the financial technology ecosystem globally.

At the moment we are still a few years from listing, and the exact form is still to be determined — especially in such a dynamic market. Right now we are still focused on growing the business, delivering exceptional customer service and leading-edge payments technology for our merchants — they're the ones truly changing the world.

–CNBC's Ryan Browne contributed to this report.

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