Tax non-compliance during the pandemic cost  the UK government £9 billion, according to a report from the National Audit  Office (NAO).
HMRC redeployed around 1,350 workers to  Covid-19 support schemes throughout 2020/21, shrinking the number of those  working on tax compliance, the NAO said.
This reduced the tax authority's capacity to  investigate people and businesses not paying the correct levels of tax,  according to the NAO.
Before the pandemic, tax revenues from HMRC's  compliance work were on average 5.2% of its total revenues. This dropped to  4.2% between 2020 and 2022 causing a £9 billion reduction in revenues.
Gareth Davies, Head of the NAO, said:
'HMRC  had to move swiftly to reallocate resources to Covid-19 schemes, as the  circumstances of the pandemic demanded. However, this directly affected its  ability to investigate cases of people and businesses not paying the right tax.
'There  is now a risk that more people ultimately fail to pay the right tax or escape  investigation or prosecution. It is concerning that HMRC's planning indicates  that non-compliance may grow following the pandemic. The next two years are  critical, and swift action is likely to be needed to stem potential losses.
'There  is little doubt that HMRC's compliance work offers good value for money, but it  needs to evaluate its performance more consistently. Improving the  effectiveness of HMRC's compliance work can help maximise the amount of money  available for public services in a challenging economic context.'
Internet  link: NAO website