R&D tax claim pre-notification: what you need to know

Author: Jen Badger Published: 21^st October, 2026

UPDATE: it was announced at Budget 2026 that the CNF will no longer be required form claims submitted on or after 1st April 2026 – details here

Pre-notification for R&D claims is required for any company wishing to claim R&D tax relief who hasn’t claimed before, or who hasn’t submitted a claim within the last three years. Although the requirement for pre-notification has been in play for over three years, we’re still seeing claimants and advisors having trouble understanding and applying the rules, and this is leading to claims being missed or rejected.

To try and help overcome this, we’ve brought together everything you need to know about claim-notification, making sure that it is at the forefront of your mind as we move into the busiest period of the year for R&D tax relief claim submission.

When should a company submit the CNF?

Companies can notify HMRC of their intention to claim R&D tax relief any time from the first day of the period of account to six months after the end of the claim period – this is known as the claim notification period. For company with a period of account longer than 12 months, this still applies, meaning that only one CNF is required for these periods of account.

Who needs to submit a CNF?

Submitting a CNF is not mandatory for all claims, but the rules around who does need to submit one are a little complicated. Pre-notification is required if:

The company has never claimed R&D tax relief before, or
The company has not submitted a claim for R&D tax relief in the three yearly prior to the end of the claim notification period, or
The only claims that the company has submitted within the three years prior to the end of the claim notification period were
- for periods starting before 1^st April 2023 and submitted as amendments to the CT600 after 1^st April 2023.
- Rejected by HMRC and removed from the company tax return.

How is the CNF completed and submitted?

The CNF is a relatively simple form, access through an HMRC portal. To fill it out you need the following information:

The claimant company’s UTR
Contact details of the main R&D contact within the claimant company
Contact details of any against involved in preparing the claim
The accounting period and period of account start and end dates
High-level summary of the R&D activities

HMRC’s guidance asks for ‘a summary of the high-level planned activities…you do not need to include evidence on the claim notification form, but you’ll be asked to give additional information before you claim R&D relief on your return’. How this section is answered will depend on what point during the claim notification window the CNF is submitted – the later it is submitted, the more in-depth information will be available about what work was done during the claim period.

What should be avoided?

While HMRC have given little feedback about what they want to see in the CNF, there is some anecdotal information available about what they don’t want to see. This includes:

Repeated wording across clients: HMRC have noticed instances where agents submit multiple CNFs for different companies, all with identical descriptions of the R&D. This may prompt further enquiries.
Overly brief descriptions: Some CNFs contain little more than “R&D was carried out.” Although such wording technically fits the requirement for “a summary of the high-level planned activities,” it is not as informative as HMRC would like to see and may be questioned.
Incomplete or nonsensical entries: A few forms have been submitted with placeholder or random text. These do not meet the requirements and will be rejected.

Can claims be submitted if pre-notification is missed?

No. HMRC will reject claims where a required pre-notification has not been submitted. HMRC have been somewhat sympathetic where genuinely exceptional circumstances can be demonstrated, but overall it’s unlikely that a claim will be accepted if the CNF is missing.

What does best practice look like for managing CNF submission?

As with everything related to R&D tax relief, robust processes and accurate records are key to success in submitting the CNF. Making sure that records are kept of each eligible company and when it submitted previous claims will enable the correct decisions to be made about whether a CNF is needed. Processes should be put in place to track claim notification periods, work out which companies need a CNF and then and submit CNFs on time and with the required information.

Alongside this, having processes in place for managing new clients and ensuring that all information about their previous claims is received and recorded to ensure a seamless transition of R&D claim work is vital.

However, having said this, there’s no downside to simply submitting a CNF for all clients as a matter of course. HMRC do not penalise companies who submit a CNF but do not them go on to submit a claim, and doing this means that no claim will be accidentally missed.

With stricter HMRC oversight, accountants and advisers need a process that leaves nothing to chance. WhisperClaims keeps you on track with tailored guidance, risk assessments and expert Advice Line support, helping you submit robust claims, and keeping you confidently on the right side of HMRC.

Book a demo today to find out how we can support you and your firm.