The Claim Notification Form (CNF) in practice: a snapshot three years on

Nearly three years after HMRC introduced the Claim Notification Form (CNF), pre-notification remains a nuanced area of the R&D tax relief process.

This week, we ran a webinar revisiting the CNF rules ahead of the March 2026 deadlines, and to help frame the discussion, we asked attendees two questions about their experience with the CNF.

The results offered an interesting snapshot of where the sector currently stands.

Confidence levels: comfortable-ish with the rules

At the start of the session we asked: “Before today’s session how confident did you feel about identifying when a CNF is required?”

The responses were as follows:

11% – Very confident

33% – Fairly confident

33% – Somewhat unsure

22% – Still unclear in some situations

So, while a good proportion of our audience felt broadly comfortable with the rules, many still encounter scenarios where the answer is not entirely obvious.

This was no surprise to us, as it absolutely reflects what we hear through our Advice Line and day to day conversations with firms – the core rules are generally understood, but identifying when the CNF requirement applies in practice can sometimes be less straightforward.

CNF issues accountants encounter in practice

Later in the session, we asked attendees whether they had experienced any CNF-related issues when preparing R&D claims.

The most common scenario by some distance was, 54% – Taking on a new client and discovering the CNF deadline had already been missed.

Other responses included:

23% – Uncertainty about whether a CNF was required in a particular scenario

8% – A CNF deadline passing before it was realised one was needed

8% – A previous claim being rejected after the deadline for the next CNF had passed

8% – Other scenarios

The prominence of the “new client” scenario is particularly notable. When firms take on an R&D client part way through the claim cycle, the pre-notification window may already have closed.

In these cases, even where the underlying R&D activity is eligible, the claim cannot proceed if a CNF was required but not submitted in time – no doubt causing frustration and disappointment all round.

Revisiting the rules ahead of the deadlines

Unlike the Additional Information Form (AIF), the Claim Notification Form (CNF) is not required for every claim. Whether a CNF is needed depends on the claimant’s circumstances and their claim history. As a result, the requirement relies on firms identifying when pre-notification applies, rather than it being automatically triggered as part of the claim preparation process.

With the March 2026 deadlines approaching, the purpose of the webinar we ran was simply to step back and recap the rules, highlight some of the situations where firms could get caught out and provide an opportunity for discussion.

We covered:

When and why pre-notification is required

How the CNF exemption criteria work in practice

Common causes of missed claims

Steps firms can take to manage missed CNF risk

One of the key messages from the discussion was the importance of having clear processes in place to identify potential CNF requirements early.

Pro-active steps to limit a missed CNF

More and more firms are choosing to submit a CNF as a precaution, even where eligibility is uncertain, particularly where there is any possibility that qualifying R&D activity may arise during the period.

At present, there is no indication from HMRC that submitting a CNF and subsequently not making a claim carries any negative consequences. In practice, this provides a simple safeguard that helps ensure legitimate claims are not lost simply because the notification requirement was overlooked.

A structured approach to claim preparation

Pre-notification is now a routine part of the R&D tax process. Revisiting the rules periodically and ensuring robust internal processes are in place can help firms ensure that potential claims are not lost simply because a CNF requirement went unnoticed. Many firms are recognising the need for a more structured preparation process to ensure that key questions are addressed consistently, and that supporting evidence is captured as the claim is prepared.

WhisperClaims provides a compliance-first framework designed specifically for accountants and advisers preparing R&D claims in-house.

Our platform guides users through eligibility costs and evidence requirements, produces structured outputs, including everything you need to complete the Additional Information Form, and provides access to expert support through our Advice Line channels.

Watch the webinar

If you were unable to join us live, you can watch the full recording by clicking below:

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And, if your firm could benefit from a structured, evidence-led process for preparing claims, WhisperClaims provides guided workflows, risk reviews and expert support to help you and your team. Book a demo to see how it works!

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