HMRC estimates that error and fraud in R&D tax reliefs was £336 million in 2020– 21, or 3.6% of related expenditure (2019–20 – £311 million or 3.6% of related expenditure). The C&AG considers the level of error and fraud estimated by HMRC to be material and qualified his regularity opinion in 2020–21 as he had first done in 2019–20. The actual level of error and fraud could be much higher as HMRC’s estimates involve judgements and assumptions.25