Rillet, a two-year-old startup that claims to be the first truly AI-native accounting platform, has secured $100 million in Series C funding at a $1 billion valuation, the company exclusively told Fortune. This milestone places Rillet among the burgeoning ranks of AI-era unicorns aiming to disrupt decades-old enterprise software giants.

The investment round was led by ICONIQ, with continued support from existing backers Sequoia Capital, Andreessen Horowitz, and Oak HC/FT. New investors joined the round as well, including Bain Capital Ventures, Sequoia Global Equities, Battery Ventures, FirstMark, Scale Venture Partners, and Creandum. This marks Rillet's third fundraise in the past year and pushes its total funding to over $200 million. ICONIQ general partner Seth Pierrepont is joining Rillet's board of directors.

For Nicolas Kopp, co-founder and CEO, this achievement is deeply personal. In an interview with Fortune, he described the company's mission as liberating CFOs from the tedious, time-consuming work that keeps them tied to spreadsheets long after everyone else has left the office. "CFOs really struggle day to day. They can't see their families on weekends," Kopp said, noting that they spend excessive hours reviewing data and creating presentations. With a background in finance and accounting himself, and a team full of similar expertise, Kopp emphasized that AI should not replace finance professionals but rather serve as an unyielding assistant. "Our message is not that we're coming after jobs. That's just not correct," he stressed. "We're positioning AI as a helper to that individual and what they can achieve."

Rillet's growth has been remarkably rapid. Kopp noted that the company launched publicly about two years ago, raised a Series A led by Sequoia last summer, and closed a Series B just weeks later—a round where new annual recurring revenue doubled quarter over quarter. The company doubled its new ARR again in the three months leading into this latest raise, and now serves more than 600 customers. These clients include some of the fastest-growing AI companies in the world—Neuralink, Skild AI, and Mercor among them—alongside a growing share of non-tech businesses. Roughly 40% of Rillet's customer base is now outside the tech and AI sectors, spanning industries like waste recycling and movie studios. Kopp described this shift as evidence that AI-native finance tools are penetrating the broader U.S. economy. "That's been really cool to see," he said.

Mercor stands out as a marquee reference customer. According to Rillet, Mercor's finance team uses Rillet's AI agents to manage a business scaling past $2 billion in annual recurring revenue with a headcount of just three. "Rillet is the clear leader in AI-native accounting infrastructure," Pierrepont said in a press release announcing the fundraise. "What stands out is how customers actually run on it—multibillion-dollar businesses operating with finance teams a tenth the traditional size, closing their books continuously."

Rillet's pitch is direct: legacy enterprise resource planning (ERP) systems—Oracle Fusion, SAP, Workday, Microsoft's Great Plains, and NetSuite—were built for a pre-AI era and are now vulnerable to a challenger built from scratch around artificial intelligence. "Some of these giants that seemed untouchable" are facing serious disruption, Kopp said, describing a wave of enterprise customers ripping out legacy systems in favor of Rillet's platform.

The core distinction Kopp draws is architectural. Traditional ERP systems were designed for humans to input and review data, a workflow that drags finance chiefs into day-to-day minutiae instead of focusing on strategy. Rillet, in contrast, is "agent-first," with AI systems capable of running hundreds of operations in parallel, executing much of the manual accounting work that traditionally consumed finance teams' time. This shift, Kopp argues, not only saves time but also produces cleaner, more consistent financial data while creating a complete audit trail. "Proving out the work layer is mission-critical for enterprise readiness," he said, asserting that Rillet is the only system combining deterministic accounting data with AI agents completing complex, end-to-end work.

Rillet has paired this pitch with credibility-building moves in the accounting establishment. Earlier this year, the company launched an alliance with EY for AI-native finance transformation, and it now partners with more than half of the Accounting Today top 20 CPA firms. Kopp traces much of Rillet's recent momentum to rapid improvements in underlying AI models. "Traditionally a very old, stodgy category," accounting has been transformed by AI. "Especially in the last six months, things started lighting on fire in a good way," he said, describing tasks that once took a human a full day now taking a couple of minutes. This frees up time for higher-level strategic work, not job loss.

The acceleration comes as the accounting profession faces a separate crisis: fewer graduates entering finance and accounting careers. Kopp sees that talent gap as part of the opportunity. AI agents can help compensate for a shrinking pipeline of human accountants even as business complexity increases. Rillet's own product development has sped up in step with its AI capabilities. Kopp pointed to instances where the customer support team, many with accounting training, has shipped feature requests within two to three hours of a customer raising them, as engineers build tools in direct collaboration with in-house accountants. "That wasn't possible six to 12 months ago."

(For this story, Fortune journalists used generative AI as a research tool. An editor verified the accuracy of the information before publishing.)