For accounting periods starting on or after 1 April 2023, the Claim Notification Form (CNF) is now a statutory requirement for some R&D tax relief claimants.
A CNF needs to be submitted to HMRC if you are planning to claim R&D tax relief for the first time, or your last claim was made more than 3 years before the last date of the “claim notification period” (see more detail below). It must be filed online within 6 months of the end of the accounting period, or the claim risks being invalid.
The form should be completed by a representative of the company or agent acting on your behalf. This is a separate requirement from the Additional Information Form (AIF).
As announced at Budget 2026, the government will introduce legislation in Finance Bill 2026-27 to remove the requirement to submit a CNF for R&D claims made on or after 1 April 2027.
In general it is correct that any company that has made a claim in any of the earlier 3x accounting periods does not need to submit CNF for their fourth accounting period in which they intend to make a claim.
However, it should be stressed that it’s three years before the last day of the claim notification period (not from the end of the accounting period). Notification must have been made by that date (e.g. an intention to make a claim for an earlier period which will ‘frank’ that later period but is not made within the six months).
Additional layers of complexity, such as the inclusion of R&D claims through amended returns, may create issues around the timing of advanced notification but in the most straight forward of circumstances the below worked example would apply.
If the company made an R&D tax relief claim for an earlier period but they submitted that claim after the last date of the claim notification period for the current year of 30 September 2026 (i.e. after the normal claim deadline but before the CT return amendment deadline), then the company will have to submit a claim notification for the current accounting period to claim R&D tax relief.
The exception to the previous step would be where the earlier and current year accounting periods form one long period of account and a claim notification has been received which covers the whole period of account.
To complete the CNF you will need:
If a CNF is required but is not submitted on time, HMRC will invalidate the R&D tax relief claim for that accounting period. Missing a CNF for one specific accounting period does not invalidate R&D claims for future accounting periods.
As announced at Budget 2026, the government plans to remove the requirement to submit a CNF for R&D claims made on or after 1 April 2027.
For accounting periods starting on or after 1 April 2023, the Claim Notification Form (CNF) will become a statutory requirement for all first-time claimants and any company that falls outside of the check process above.
Yes – The Additional Information form became a statutory requirement for all R&D claims submitted to HMRC on or after 1 August 2023, regardless of how many previous claims the company has made or when those claims were made.
Yes. If a Claim Notification Form was required to be submitted during the notification window, when the actual claim is subsequently filed with HMRC, the Additional Information form must also have been submitted on or before the filing of the tax return with the R&D claim. After 1 August 2023, if a claim is submitted without the Additional Information form, HMRC will write to you to inform you that they have removed your claim for R&D relief from your tax return.
To compound the issues in this already confusing area, HMRC itself published incorrect guidance in the Corporate Intangible Research & Development Manual (CIRD183000) on 8 Sept 2024. The correction wasn’t made until 17 October, six weeks later.
This error provided an inaccurate interpretation of the requirement for a claim notification and how exemptions were to be applied.
For clients affected by the incorrect information, HMRC has agreed an appeal process and will allow claims for an accounting period without a CNF where the following apply:
A company made a valid claim to R&D in an amendment to a return for an accounting period beginning before 1 April 2023, which was submitted to HMRC between 1 April 2023 and 30 November 2024 inclusive.
The accounting period for which a Claim Notification was not delivered, but ought to have been, had a claim notification period ending between 8 September 2024 and 30 November 2024.
