Murphy is well known for his estimates that "£25 billion is lost annually from tax avoidance".[4] This is substantially larger than HM Revenue and Customs' estimates of the tax gap, and his estimate has been dismissed by HMRC.[5] His methodology has been criticised by other groups, including the Oxford University Centre for Business Taxation in their December 2012 publication The Tax Gap for Corporation Tax.,[6] and right-wing think tanks like the TaxPayers' Alliance which claim he has failed to take into account double taxation relief on overseas profits and for including taxes not paid in the same tax year as the profits were earned,[7] and the Institute for Fiscal Studies which cited his estimate of the corporate tax gap for the TUC as one which was "likely overstated (possibly by a wide margin)".[8]