Restauranteurs and those in the motor trade are to be targeted in a crackdown by the taxman.
Special taskforces focussing on South Wales have been set up by HM Revenue and Customs (HMRC).
The taskforces are expected to recoup millions of pounds in unpaid tax.
The teams will visit traders to examine their records and carry out other investigations.
The Exchequer Secretary to the Treasury, David Gauke, said: “At a time when we are trying to rebalance the public finances and most hard-working people are making a contribution by paying the right tax, it is just not fair that a small minority try to dodge their responsibilities.
“These new taskforces are funded by the Government’s investment in HMRC of over £900m to crack down on avoidance and evasion. Their dedicated teams are on track to collect more than £50m from tax avoiders and evaders through the taskforces launched last year and expect to collect £30m in unpaid taxes through those launched today.”
HMRC’s Mike Eland, Director General Enforcement and Compliance, said: “Everyone needs to pay the taxes they owe in full – these new taskforces will help us crack down on the minority who have chosen to break the rules. If you have paid all your taxes you have nothing to worry about. But deliberately evading tax you should be paying can land you with not only a heavy fine but possibly a criminal prosecution as well.
“This is not an empty threat – HMRC can and will track you down if you choose to break the rules.”