Rillet Raises $100 Million to Challenge Accounting’s Legacy Stack

Rillet has raised a $100 million Series C at a $1 billion valuation, backing its push to make AI agents a working layer inside corporate accounting. The company says the agents can handle much of the manual work that keeps finance teams inside legacy systems, while accountants retain the ability to examine the result.

ICONIQ led the financing, which pushed Rillet’s total funding past $200 million. Sequoia Capital, Andreessen Horowitz and Oak HC/FT returned; Bain Capital Ventures, Sequoia Global Equities, Battery Ventures, FirstMark, Scale Venture Partners and Creandum also invested.

The round’s investor roster

• Lead investor: ICONIQ.
• Returning investors: Sequoia Capital, Andreessen Horowitz and Oak HC/FT.
• New investors: Bain Capital Ventures, Sequoia Global Equities, Battery Ventures, FirstMark, Scale Venture Partners and Creandum.

The investment was fast, but not a cold start

Kopp said the Series C came together within 48 hours after Rillet discussed its recent growth with investors. ICONIQ’s Seth Pierrepont said the firm had also backed the Series B and had watched the Rillet team deliver over the prior year. The growth metric depends on the account: TechCrunch reported that annualized revenue doubled in the prior quarter, while Fortune reported that new annual recurring revenue doubled in the three months before the raise.

A replacement pitch, not an add-on

Kopp’s argument is about how the software is built. He characterizes traditional enterprise resource planning, or ERP, products as systems designed for people to enter and review data. Rillet, he says, is built agent-first: AI systems can run many accounting operations at once, with people working alongside them. Rillet is therefore pitching an alternative to the system where accounting work is recorded, rather than a tool that simply assists an existing one.

Rillet says customers are replacing products from Intuit, NetSuite, Sage Intacct, Oracle, SAP, Workday and Microsoft. Kopp said roughly half of customers came from Intuit, 30% from NetSuite and Sage Intacct, and 20% from the remaining group. Those are company-supplied customer-origin figures, not measures of those vendors’ market share.

The control layer is part of the sale

Automation in accounting creates a second requirement: people need to see how the system reached a number. Rillet says its governance feature lets accountants inspect agent decisions, including the numbers retrieved and calculations used. Kopp said the company had to compress the agent’s activity into a form people could understand.

Kopp also said customers can route requests to foundation models including OpenAI and Anthropic, while Rillet prevents those models from training on customer data. He said customer data is not cross-trained between clients. These are Rillet’s claims about how its product handles data.

Kopp said regulations for public companies require another human to approve each transaction made by an AI agent. That requirement is narrower than a general ban on automation, but it places human review directly inside the kind of workflow Rillet wants to redesign.

Customer count offers a test of the pitch

Rillet says it serves more than 600 customers, including public companies and the NFL Hall of Fame, and has an alliance with EY to introduce AI tools to the auditing firm. The customer roster and accounting-firm relationship put the company’s replacement claim in settings where auditability and review are not optional product extras.