It also transpired, when we questioned the Department about the size of the tax gap in the construction industry, that HMRC does not assess and publish the relative size of the tax gap across different industries. The construction industry has traditionally had quite high levels of non-compliance. HMRC introduced the Construction Industry Scheme to tackle the risks in the construction sector but it has not assessed the tax gap in the sector since.19 Notwithstanding the lack of a tax gap estimate for different industries, HMRC has intelligence on the levels of non-compliance in different sectors, such as in the case of buy-to-let landlords.20 HMRC uses such intelligence to inform the targeting of its campaigns, where it contacts large numbers of taxpayers in a specific sector and invites them to revise their tax filings. A number of taxpayers that do not take action will then be subject to HMRC investigations.21 The completeness of the tax gap