Croydon and Tadworth addresses were raided yesterday in connection with a £51m money laundering investigation.
Eight members of the same family were arrested following a host of dawn raids.
A HMRC spokeswoman said all eight family members have been bailed until July 29.
She said: “The business they were associated with was in the IT trade.”
The arrests took place in Burton upon Trent, Staffordshire and Tadworth, Surrey as 50 Her Majesty's Revenue and Customs officers searched properties for evidence.
Three men and four women were arrested in Burton upon Trent, two residential properties and one business address was searched.
Another 44-year-old man was arrested in Tadworth. A business address in Croydon was also searched.
Colin Booker, Assistant Director, Criminal Investigation, HMRC, said: “Money laundering and associated tax evasion is a serious offence and is usually the result of major organised crime gangs trying to clean up their dirty cash.
“We have worked closely with Staffordshire Police in this operation and will continue to pursue those who operate outside the law and attempt to evade tax.
“Anyone with information about people who may be involved in tax fraud can contact the Customs Hotline on 0800 59 5000.”
Computers, personal and business records were removed during the searches, and investigations continue.