Forty-eight hours. That is how long it took Rillet, an American AI accounting startup, to raise 100 million dollars (around 86 million euros) and reach a valuation of one billion. The company, says its founder, was not looking for money.

The story goes like this. A few weeks ago Rillet held a board meeting and showed investors how it was growing: annualised revenue doubled in the last quarter alone, new clients arrived including listed companies, and a deal was signed with auditing giant EY. After the meeting, messages and phone calls started flying - and two days later the company was worth a billion.

What is being sold here is not software, but a shortage. The US is short of accountants, and that is not new - the number of accounting graduates has been falling since 2010. According to a recent report, 61 percent of finance executives had trouble finding staff in the past year. When a profession runs out of people, anyone offering a substitute gets an investor.

Nicolas Kopp, co-founder and CEO of Rillet, claims clients are not testing - they are ripping out their existing systems directly. Fifty percent of his customers come from Intuit, thirty percent from NetSuite and Sage Intacct, and twenty percent from Oracle, SAP, Workday and Microsoft. "AI is going to hit these old players hard," he says.

The investors, of course, talk like investors. Seth Pierrepont of Iconiq, who led the round, says the deal came together fast but "was not a cold start", because Rillet had already proved it can beat firms that have held the category for decades. Julien Bek of Sequoia announces that "agentic finance operations" could become one of the biggest software opportunities of this era. Anyone who put money in is obliged to sound like this - that is not evidence, it is part of the transaction.

More interesting is the part rarely mentioned in announcements like this. About three months ago Rillet released a feature letting accountants check every decision the algorithm makes - which figures it pulled and how it calculated them. That is not marketing, that is an admission that the system has to be auditable before it is allowed anywhere near the books. US rules still require a human to approve every transaction made by an agent.

Kopp does not think mass layoffs of accountants are coming - a Stanford study recently found no broad displacement of jobs so far. The US Bureau of Labor Statistics forecasts that demand for accountants will grow by at least 5 percent by 2034. Whether that holds once the agents learn a bit more is a question no investor has any interest in answering honestly.