HMRC introduced the additional information form on 8 August 2023. This must be submitted for all claims for Research and Development (R&D) tax relief or expenditure credit.
HMRC are aware that customers are unable to complete both boxes 655 and 657 on the CT600 and may get the following error:
Error 9283 — Box 655 can only be completed if at least one of the boxes 670 or 680 is greater than 0 (zero).
If you get this error, do not make entries in boxes 655 and 657.
You must still submit the additional information form to make a valid R&D expenditure credit claim.
HMRC will update the service in April 2024 to resolve this issue.
More information regarding the new rules process of claiming R&D tax reliefs recently came into force and these can be found on https://www.gov.uk/guidance/corporation-tax-research-and-development-rd-relief#before-you-claim