The Spending Reviews in 2020 and 2021 enabled HMRC to increase its compliance staffing. In 2021–22, CCG recruited mainly senior staff to undertake compliance work. Around the same time, HMRC was reducing its frontline customer service workforce, most of whom were in lower grades. These two changes were the main factors which led to the proportion 32 C&AG’s Report, para 2.22 33 Q 37: C&AG’s Report, para 2.26 34 Qq 12, 38 35 Q 56 14 of HMRC’s staff in more senior grades increasing from 41% to 53%.36 This change in grade mix increased HMRC’s salary costs by over £100 million over the period 2019–20 to 2023–24. We challenged HMRC about the increase in its staff costs. It said the grading of compliance staff “reflects the challenges we have in recruiting, training and retaining the staff that we need to do that work.” 37