Deloitte Cyprus has been accused of signing off on faked documents that enabled sanctioned Russian billionaire Roman Abramovich to conceal around $672 million. The documents erased superyachts, mansions, and private jets from his company accounts between 1999 and 2013.

The evidence comes from the Cyprus Confidential investigation, involving more than 500,000 documents leaked to the International Consortium of Investigative Journalists and analyzed by global news organizations including the BBC and The Guardian.

Ruth Prickett graduated from Cambridge University with a BA hons in History and has specialized in business and finance journalism for the past 20 years. She was editor of Financial Management, the magazine...