HMRC said on Wednesday that it had raided six addresses in the West Midlands and South East in a probe led by the Canada Revenue Agency.
The investigation relates to a suspected $55m tax evasion and money laundering fraud.
HMRC deployed 40 officers to search addresses in London, Redditch, Birmingham, Stratford Upon Avon and Kenley areas on Tuesday, while other searches were being carried out in Ontario.
The Revenue said documents, computers and mobile phones were seizes during the operation.
Paul Fisher, assistant director of HMRC’s fraud investigation service, said, "Tax fraud is a threat to public funding across the globe.
“As this operation shows, HMRC regularly work with our international partners to both tackle, and assist others in tackling, suspected tax fraud.
“We would ask anyone with information to contact our Fraud Hotline on 0800 788 887.”