A 58-year-old man from Stevenage has been arrested on suspicion of tax fraud as part of an operation which saw 50 HM Revenue and Customs officers search business premises and residential addresses in towns including Stevenage.
Officers seized computers and business and personal records, and six people were arrested on suspicion of promoting fraudulent loan charge arrangements.
Loan charges are the government's way of getting people who have avoided paying income tax and national insurance to pay up.
A HMRC spokesman said: "We strongly encourage people not to use loan-busting schemes and methods. They clearly don't work and people run the risk of losing more money and being involved in fraud. As we always say - if it looks too good to be true, then it undoubtedly is."
All six people arrested were interviewed by HMRC officers and have been released while investigations are ongoing.
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