Fifteen years later, one of those early ideas is stepping into the spotlight, providing what Stripe has come to see as a new pillar to its business. 

Stripe Billing, for years a slept-on prototype at the San Francisco company, has become the engine of Stripe’s Revenue and Finance Automation suite. At the end of January, the group crossed $500 million in annual revenue run rate. Though the Collison brothers wrote the first iteration of a billing product before Stripe launched, Stripe Billing didn’t come to market until 2018. 

“It was something we underestimated for a very long time,” said John Collison, Stripe cofounder and president. “I think it’s only recently that we started viewing it as the main second business.”

With customers like Atlassian, OpenAI, Anthropic, and AMC Networks, Stripe Billing essentially handles a company’s recurring payments and usage-based services like pay-as-you-go cloud-based software. (If you’ve paid for an AMC+ subscription to watch The Walking Dead, you’ve used Stripe Billing.) It’s a notably different market and technology than the bread-and-butter online payments Stripe processes. Stripe Billing’s rise means the company has new competitors in a fundamentally different business—and potential to embed even more deeply into large enterprises and fast-growing AI startups.

For Stripe, one of Silicon Valley’s most scrutinized private companies and long-stalked by IPO watchers, the growth of the billing business clearly represents a key puzzle piece to the company’s future. (Collison affirmed the company’s commitment to building a strong business when asked about plans for going public.)

After years of growing quietly, Stripe thinks the time has come for billing to find its light. Stripe billboards have been springing up across the country in what Stripe CMO Jeff Titterton described in a statement as “our biggest brand marketing push yet.” The campaign has featured high-profile customers and, Titterton added, over time has “expanded to put Billing center stage.” 

An invisible internet giant

In some sense, Stripe is paradoxical—an invisible giant, simultaneously everywhere, though you probably don’t notice it. 

If you’ve bought crewnecks from Amazon, curtains from Wayfair, or shoes from H&M, your payment was processed through Stripe. If you’ve ordered pizza from Postmates, gotten groceries on Instacart, or booked an Airbnb—all those payments were processed through Stripe.

In 2023, Stripe surpassed $1 trillion in total payment volume, serving millions of businesses, from Fortune 500 companies to startups and small businesses. The years since the pandemic have been a bit of a roller coaster: In March 2021, the company hit a $95 billion valuation, which slid in the post-pandemic slowdown.

Stripe declined comment on its financials and directed Fortune to its 2023 annual letter, which stated that Stripe was cash-flow-positive in 2023 and expected to be again in 2024.

Despite the fluctuations, Stripe remains high on Silicon Valley’s mountain of unicorns, and the company’s core business remains intrinsic to the modern internet economy. As the internet has evolved, billing has also become an increasingly important part of the digital economy—and an area in which Stripe sees opportunities. Sharmeen Browarek Chapp, Stripe’s head of product for the Revenue and Financial Automation business, believes that billing today is where online payments were ten years ago. “We’re at the same inflection point,” she said. 

Handling different types of payments, such as pay-as-you-go, is an increasingly critical feature for companies today, said Chapp. “If businesses can’t stay up to speed, it holds them back.”

And though they’re both, well, money-related, billing and payments are different. 

“There’s a whole different side of accounting that you have to deal with,” said Tara Seshan, former head of product for Stripe Billing. “Payments are often in the cash-based accounting world. Billing is often the interface between your real revenue accounting, your accrual-based accounting world and your cash-based world. So, you’re having to think about a whole bunch of complexities… It’s a huge headache. There’s a lot of edge cases, and it’s why businesses shouldn’t build their own.”

That’s not to say they have nothing in common. Billing and payments both, for example, hinge on trust. (Stripe said that, during Black Friday and Cyber Monday in 2024, its API maintained an uptime of more than 99.9999%. That means you’re more likely to get struck by lightning than hit Stripe downtime.) But billing’s demands are ultimately very specific. 

“At the end of the day, billing is more of a software play,” said Jordan McKee, global director of S&P’s Fintech Research and Advisory Group. “You’ve got to have a lot of capabilities at play to collect revenue from your customers on a recurring basis. You need to be able to support different pricing models and code that in, whether it’s recurring billing, usage-based, or tiered.”

Billing’s complexities

Collison is upfront about how tricky billing can get. 

Here’s an example, Collison says: If we sit down and start a telephone company, how hard can managing pricing be? It starts out simple with, say, $20 monthly individual plans. But over time, you have the complexities that come with family plans, customers joining mid-month, and international travel. 

“Suddenly, we have an extremely complex engineering problem that comes from making very reasonable business choices,” he said. 

In short, billing can become a labyrinth, built up over time in a way that’s interconnected and sometimes intractable. 

“It’s very easy for things to quickly get complex,” Collison said. “It’s sort of like orbital mechanics, where everything has an effect. ‘We just want the rocket to go to the moon. How hard can it be?’ Well, you’ve got to take into account gravity, and so on.”

In the early days of Stripe Billing, the project was less Mission Control and more 30 Rock. 

“I often describe how working on Stripe Billing was like working at SNL, in the sense that everyone is having nightmares every week, trying to get the show on the road and ship this feature,” said Seshan, who was leading Stripe Billing from 2017 to 2019. “It all felt like improv a bunch of times.”

One especially harried day, Seshan and the billing team printed out a deluge of launch and integration documents, pasting them all over a conference room.

“We were rewriting the examples on a whiteboard,” said Seshan. “I hadn’t showered in three days, neither had anyone else. It was very SNL: A guy on our team had come to give us a pizza. He opened the door and was like: ‘It smells terrible in here!’”

Stripe Billing has come a long way since, especially in the last three years, as the product has found a notable home among fast-growing AI startups, from OpenAI and Anthropic to Perplexity and MidJourney. (Fortune has a business partnership with Perplexity.) For MidJourney—known as a leader in generative AI images—Stripe Billing has been essential, said MidJourney CFO Nadia Ali. In 2023, she says, MidJourney’s $200 million in ARR ran through Stripe Billing. 

“The floodgates just opened,” Ali told Fortune. “We really weren’t expecting that amount of interest at all. Because we were using Stripe, it allowed us to really be able to scale quickly in terms of our accounting, for example, where we use Stripe for revenue recognition, all our tax reporting. That made a huge difference in how my team is structured right now—we’re able to stay very, very lean.”

MidJourney uses usage-based billing (a concept Stripe demos in an online spaghetti-eating game). It’s a capability essential for an AI company at a time in the boom where there’s a lot of angst about what it takes to stay soaring as a high-flying AI startup. 

“We hear from our users all the time that it can take up to six months for them to make a small change in their billing,” said Stripe’s Chapp. “Think about these AI companies and how much they’ve grown in the last two years: If every change they made took six months, they wouldn’t exist.”

That’s not to say only AI startups need billing help. Collison has been struck by the extent to which billing has attracted interest up and down the corporate food chain. (Atlassian, whose market cap comes in around $82 billion, uses Stripe Billing across all its products.)

“A decade ago, people would have said Stripe’s really popular with startups, and part of what it does is for developers, helping them get to market faster,” Collison told Fortune. “That’s where we got our start, the intuitive sense that this was something very helpful for startups. But we didn’t really have a view of all these more established companies. I think what emerged—and it was striking—is that almost all large enterprises are dissatisfied with their current billing.”

Stripe’s future

Stripe faces a number of billing competitors, said S&P Global’s McKee, who cited Zuora, Chargebee, and Recurly. Adyen is also in the mix, even though Stripe still has an edge with earlier stage companies. 

“If I were a competitor, I might try to throw some shade on Stripe for having its hands in too many things, for maybe not being as focused or as dedicated to billing as another company,” said McKee. But he credits Stripe for making the product incredibly approachable: “You don’t have to be an engineer or an expert coder to bring this thing to life.”

Stripe’s broad marketing push around billing is similarly sleek and approachable. One monochromatic purple-tinted billboard shows The Walking Dead on a TV set, zombies breaking through the windows behind it. In a zombie play-on-words, it reads: “AMC+ makes subscriptions with Stripe a no-brainer.” 

To McKee, the big question is this: How big can billing really get? “Does it ever make sense to actually spin this out, and it becomes an independent company still with like these arms-length agreements with Stripe,” he wonders.

Time will tell, but one distinctly possible scenario could see Stripe Billing following a path similar to Amazon’s AWS cloud business — a stalwart giant in its own right, linked to something even more expansive. It’s been a runaway success for Amazon, whose share price and profit have surged in the years since the retailer launched its cloud business.

Collison isn’t letting on whether billing is part of the gateway to a possible IPO, but he’s clear that billing is a place where Stripe’s looking to the future. “We very much like the idea of tracking profitable and self-funding it, so we’re not subject to the whims of one year,” he said. “We have our ten-year roadmap for billing, and we’re going out and executing regardless of what anyone thinks.”

Over the coming months and years, it’ll be easy to forget that billing began as an experiment, started before Stripe as we know it even existed. But perhaps answers to Stripe’s much-anticipated future lie in its past—like Stripe itself, hidden in plain sight, just waiting to come into focus.