A financial adviser and five other people have been arrested and bailed during an inquiry into allegations of a £4 million tax fraud.
HM Revenue and Customs officers, supported by West Mercia Police, detained four of the suspects in Telford and Wolverhampton last Thursday.
Border Force staff assisted in the arrest of two people at Birmingham Airport on Saturday.
HMRC said the suspects, aged between 37 and 54, had been arrested as part of an investigation into a suspected Pay As You Earn tax evasion and money laundering fraud.
Richard Wentel, Assistant Director, Criminal Investigation, HMRC, said: “This is an investigation into suspected tax fraud on an industrial scale, attacking the PAYE system and associated money laundering."
During the inquiry, four domestic addresses, five vehicles and two business premises have been searched.
Computers, mobile phones, business records, and several high performance vehicles have also been seized pending further inquiries.