HMRC targets firms offering deals that stretch law to limit Promoters of aggressive tax avoidance schemes will be forced to disclose their client lists to inspectors under a government crackdown, ministers will announce today. Following a wave of revelations about the financial loopholes used by the rich and famous to legally side-step hefty tax bills HM Revenue and Customs is set to target companies who offer deals that stretch the law to its limits. Treasury Minister David Gauke will tell the Policy Exchange think-tank that scheme operators will be "named and shamed" for sharp practice. Officials often hit a dead-end when investigating schemes that are based off-shore but, under the proposals, UK promoters will be made to hand over customer databases. That information will be used to formally warn clients directly about the deals they have signed up to and to work out how much tax they owe if the scheme fails. Under the reforms, which will go out to consultation, a promoter who has been penalised for not complying with the rules will also have to provide extra information to HMRC on all of their schemes, not just the one they were reprimanded for. Mr Gauke will say: "We are building on the work we have already done to make life difficult for those who artificially and aggressively reduce their tax bill. These schemes damage our ability to fund public services and provide support to those who need it. They harm businesses by distorting competition, they damage public confidence, and they undermine the actions of the vast majority of taxpayers, who pay more in tax as a consequence of others enjoying a free ride. Last month, comedian Jimmy Carr admitted to making a "terrible error of judgment" after it emerged he used a complex scheme to reduce his tax bill. The K2 tax-avoidance scheme Carr is said to have used enables members to pay income tax rates as low as one per cent. He was one of a number of high-profile cases of people using financial loopholes to legally avoid large tax bills. The Treasury estimates that 14 per cent of all unpaid tax income is due to aggressive avoidance schemes. Although not illegal, ministers are determined to clamp down on them.