We asked whether HMRC needed more resources to catch up on the impact of the pandemic and to keep the tax gap from growing, and whether it was looking to recruit more. HMRC acknowledged that it will be more challenging to maintain the tax gap than it has been in the recent past but did not indicate what contingency plans it had if its resources were insufficient.43 HMRC told us that it will be gradually reintegrating staff from COVID-19 work to tax compliance between April and September 2023.44 It also told us that it has recruited 4,800 staff to its compliance group in the past two years. However, it takes up to four years for new staff to be fully trained and to gain enough experience to be fully effective, due to the complex nature of tax legislation and investigations which require skills ranging from technical tax knowledge to project management.45 HMRC also argued that it has up to 20 years to pursue cases of suspected non-compliance during the pandemic. However, this only applies to cases of suspected fraud. For errors the period is less, and in some cases HMRC cannot go back more than four years.46 39 Qq 82–83, 93–95 40 Qq 35–36, 41, 81, 84 41 Qq 35, 85; C&AG’s Report, para 12 42 C&AG’s Report, para 18 43 Qq 44, 85–87 44 Q 43 45 Qq 44, 80; MFP0001 46 Qq 25, 85–87 14 Managing tax compliance following the pandemic