Given that HMRC has never used the special measures regime, we asked HMRC how it can know that it is an effective deterrent. While HMRC recognised that it could not demonstrate that special measures has had a deterrent effect in any specific case, it argued that there is a broad body of contextual evidence supporting the claim that special measures deters egregious non-compliance. It credits a big drop in the proportion of the large business tax gap that stems from tax avoidance or evasion to the deterrent effect of special measures. It also noted that it carries out regular, thorough risk reviews of the large businesses it works with. HMRC said that it has assessed over half of businesses as low risk, with only 10 considered high risk.22