When do I need a Claim Notification Form (CNF) for R&D?

The CNF is a separate requirement from your Corporation Tax return and the Additional Information Form (AIF). The purpose is to notify HMRC that your company intends to claim R&D tax relief for the relevant accounting period. The notification requirement was introduced as part of HMRC’s aim to improve compliance and reduce error and fraud in the R&D tax relief regime. 

Do you need to submit a Claim Notification Form?

A Claim Notification Form (CNF) is required if you are a first-time claimant or a returning claimant, and you will not be submitting your final R&D claim within 6 months of the end of your accounting period.

Your company must submit a CNF if:

• You’re making your first ever R&D tax relief claim for a period of account beginning on or after 1 April 2023, or
• You have not made a valid R&D tax relief claim within the three years ending on the last day of your claim notification period.

When is the CNF deadline?

The claim notification period starts on the first day of your period of account and ends six months after the end of that accounting period.

An example of this would be, if your accounting period ended on 31 May 2025, the deadline for submitting your Claim Notification Form (CNF) would be 30 November 2025.

If the CNF deadline is missed, it will prevent you from making a valid R&D tax relief claim for that accounting year.

When is a CNF not required?

You do not usually need to submit a Claim Notification Form if you made a valid R&D tax relief claim within the previous three years.

There are two important exceptions. You may still need to notify HMRC if:

• HMRC rejected your previous R&D claim by removing it from your Company Tax Return, or
• Your previous claim related to an accounting period beginning before 1 April 2023, but it was submitted by amending your Company Tax Return on or after 1 April 2023. Under HMRC’s transitional rules, these amended claims do not count towards the three-year exemption.

Because the notification rules depend on both the timing and method of previous claims, it’s worth checking your filing history before assuming a CNF isn’t required.

Remember that submitting a Claim Notification Form does not replace the requirement to submit an Additional Information Form (AIF) before or on the same day as your Corporation Tax Return containing the R&D claim. Both requirements must be met where applicable.