Experts are warning that the UK tax authority is more inclined to prosecute evaders as figures show millions of pounds of unpaid tax has been recouped.
Follow-up enquiries have added millions to the collections made following high-profile disclosure campaigns.
Criminal investigations have been launched into 10 people with offshore accounts and six in medical trades.
Maximum fines for tax evaders have recently increased, but can be reduced for those who come forward voluntarily.
“Criminal investigations have not been the weapons of choice for HM Revenue and Customs, but now they are part of the armoury,” said Gary Ashford, representative for the Chartered Institute of Taxation.
Tax evaders include “chip shop owners, taxi drivers and landladies”, HM Revenue and Customs (HMRC) has said. It has been set targets by the government to harvest unpaid tax.
The original campaign aimed at evaders with offshore accounts was launched in 2007 and gathered £400m after 45,000 came forward.
Subsequent inquiries have brought in another £91m and 1,000 enquiries are continuing, the BBC has been told.
“This is proof of HMRC’s determination to increase the number of prosecutions we take forward in all areas” Chris Harrison HMRC
A second campaign was launched in September 2009. This garnered £85m from 5,500 disclosures. Follow-up inquiries yielded another £6m.
Ten criminal investigations are ongoing, although these will not necessarily lead to prosecutions.
New penalties were introduced in April which raised the maximum fine level for those with offshore accounts to 200% of unpaid tax, in addition to the repaying the tax owed.
Mr Ashford said HMRC was taking a “very tough line” against these evaders.
The tax authority has also threatened to publish the names of people who deliberately evaded tax.
This could have serious implications for those in medical professions who were uncovered as part of a campaign by HMRC targeting that sector, according to Mr Ashford.
Some £10m has been gathered from 1,500 disclosures during the campaign. Six criminal investigations have been launched.
Medical professionals who admitted unpaid tax before 30 June could pay past tax, plus interest, and a penalty of 10% of the unpaid tax.
Mr Ashford advised evaders to make a disclosure, as they could still reduce the penalties they faced by coming forward voluntarily.
More recently, HMRC has launched tax payment campaigns against plumbers and restaurant owners.
“We are confident that these and more cases will be taken forward in the future,” said Chris Harrison, HMRC criminal investigations deputy director.
“This is proof of HMRC’s determination to increase the number of prosecutions we take forward in all areas. We are committed to ensuring everyone pays what they owe so that the maximum is available to spend on public services used by everyone.”