Wise, the UK-based international money transfer service and darling of the London fintech scene, has confirmed it is answering questions from Belgian prosecutors investigating money laundering, sending its shares tumbling.

In a statement to the stock market, Wise said it was “currently working with the Brussels prosecutor to respond to queries about our business, as we routinely do with regulators and law-enforcement authorities.

“His office’s inquiries are still incomplete and no specific findings have been shared with us to date.”

Shares in the company fell nearly 20% at one point on Monday before closing down 8%, as investors digested official confirmation of discussions with the Belgian prosecutor’s office.

The London-based firm, which has 19 million customers, processes 4.7m transactions a day and is valued at more than £8bn, issued the statement in response to a report by the Bureau of Investigative Journalism (TBIJ).

The report claimed Belgian authorities were investigating whether Wise accounts had been “used by criminals to launder the proceeds of fraud, corruption and drug trafficking”.

Prosecutors in Belgium reportedly opened the investigation last year, on the basis that Wise accounts had featured in hundreds of requests for cross-border help in criminal proceedings from more than 30 countries across Europe.

The transactions under investigation amounted to €500m (£433m).

According to the report, authorities in Belgium – where the company’s European operations are located, in Brussels – have said they are investigating “indications of non-compliance with anti-money laundering legislation”.

The Guardian has approached Belgium’s central directorate of the fight against serious and organised crime (DJSOC) for comment.

“Like every financial institution, we face the reality of increasingly sophisticated bad actors attempting to exploit our platform, and we continually invest in tech-enabled systems and teams to stay ahead of ever-evolving threats,” Wise told investors.

“We start by verifying customers before they open an account and continue monitoring hundreds of data points in real time as customers use our products, with teams reviewing transactions, offboarding customers when needed, and proactively reporting suspicious activity to law enforcement.

“We take our responsibility incredibly seriously. Around one-third of Wise’s global team is dedicated to protecting our customers from financial crime and this focus is shared across all of our teams.”

Formerly known as TransferWise, the company specialises in rapid cross-border payments. Its float in 2021 made billionaires of its co-founders.

As of last month, London is host only to the company’s secondary listing after Wise moved its primary trading location to the US.

In 2024, the company’s co-founder and chief executive, Kristo Käärmann, was fined £350,000 for deliberately failing to inform the City regulator of “significant tax issues”.