$1bn start-up Rillet makes London its first European base

Rillet, a US start-up that makes accounting software with built-in AI agents, has opened an office in central London. It is the company’s first major move into Europe, Rillet said on Monday.

Customers in the UK and the rest of Europe already account for 15% of Rillet’s new annual recurring revenue, the company said. They include AI image firm Black Forest Labs and software company Temporal.

Rillet makes ERP software, the systems companies use to run their finances. It says its product keeps a company’s accounts up to date in real time. It also lets AI agents do some of the work of closing the books at the end of each month.

UK firms started using Rillet before it had any staff in the country, the company said. Many European finance teams still close their books on older systems, it added.

“Within a year of launching in the US, we already had finance teams in the UK running on Rillet,” said Nicolas Kopp, Rillet’s chief executive and co-founder.

Those customers set up the software from across the Atlantic, with almost no marketing from Rillet, Kopp said. A local office will help the company understand what they need, he added.

Rillet has already signed its first UK hires in sales, deployment, and customer support. It plans to build a full team in London, but did not say how many people it will hire.

The aim is to copy its US approach, the company said. A local team helps finance teams test the software, get it running, and then supports them once it is live.

Black Forest Labs, which makes AI image models, is one of the European customers. Its chief financial officer, Dave Arkell, said the company wanted AI built into the design of its finance software, not added on top.

“We chose Rillet for our ERP because they matched that ambition,” Arkell said.

The expansion comes less than three months after Rillet raised $100m at a $1bn valuation. ICONIQ led that round, with Sequoia and Andreessen Horowitz also investing.

Rillet now has nearly 1,000 customers in 75 countries, the company said. In August, it reported more than 600. It also said that its international new revenue more than tripled from one month to the next, but did not give the months or the amounts.

In October, LinkedIn named Rillet 22nd on its 2026 list of the top 50 US start-ups.

Rillet also plans to lean on the accounting firms it already works with. It has alliances with EY and RSM. It also works with more than half of the 20 largest US accounting firms, as ranked by trade magazine Accounting Today.

Many of those firms have large practices in the UK and Europe. Rillet said the links will help it build trust and grow across Europe, the Middle East, and Africa.