Question to the HM Treasury:

To ask the Chancellor of the Exchequer, what proportion of (a) Research and Development Expenditure Credit and (b) Research and Development tax relief for small and medium-sized enterprises claims were disallowed in each of the last five years for which figures are available; and what the most common reason was for a claim being disallowed in each of those years.

HMRC do not publish the proportion of R&D claims disallowed and the reasons for disallowing them.

HMRC publish the estimated amount of R&D tax relief claimed and the estimated number of claims. The latest figures for 2021-2022 are published here: Research and Development Tax Credit Statistics September 2023.