R&D Claim Notification Explained: Rules, Deadlines & How to File

Submitting your R&D claim notification form is one of the most important parts of the R&D tax credit claim process. Why? Because not only does it position your claim as compliant right off the bat, but it also helps to reduce scrutiny.

What is R&D Claim Notification?

An R&D Claim Notification is the formal process where your business informs HMRC that you’re planning to claim R&D tax relief.
To do this, you need to submit an R&D claim notification form (CNF). Your notification could be invalidated if you fail to submit it within 6 months after your period of account ends.

Why Do I Need to Submit an R&D Claim Notification?

R&D notification is a requirement by HMRC that helps ensure your claim is compliant.

It lets HMRC know that you’re planning to claim R&D tax credits, and gives you a smoother claims process.

Does My Business Need to Complete an HMRC R&D Claim Notification Form?

You’ll need to notify HMRC if your accounting period begins on or after 1 April 2023 and:

• You’ve never claimed R&D before
• You submitted a claim which was made more than three years before the last date of the claim notification period
• You submitted a claim within the past three years but it doesn’t meet certain criteria (see below)

If your R&D claim is for a financial year that started before 1 April 2023, and you submitted it late, you don’t need to worry about the rule that checks whether you’ve made a claim in the last three years.

Error in HMRC’s Guidance:

HMRC accidentally published incorrect information in their guidance in 2024 which misled some companies into thinking they didn’t need to submit a claim notification form for R&D.

To correct this, HMRC introduced an ‘administrative easement‘, meaning they will still accept R&D claims from affected companies even if they didn’t notify, as long as:

• The claim was submitted as an amended return between 1 April 2023 and 30 November 2024
• The period for notifying about your claim ended between 8 September 2024 and 30 November 2024

To apply to HMRC for the easement, you or your agent must email the R&D Policy team at randd.policy@hmrc.gov.uk with the subject line “CIRD 183000 notification”, and include:

• Evidence of authority to act on behalf of your company (if an agent)
• Your company name
• Your company unique taxpayer reference
• The date that you submitted the amended return containing the R&D claim
• The accounting period that was not notified as a result of HMRC’s error
• The period of account that your accounting period falls into

What are the Deadlines for Submitting an R&D Notification?

If your period of account starts on or after 1 April 2023, HMRC requires you to submit your notification within six months following the end of your period of account.

How Long is the Claim Notification Period?

The claim notification period:

• Finishes six months after your period of account ends
• Begins on the first day of your period of account (financial year)

If your financial year is over 12 months, it will cover two or more ‘accounting periods’. You still only need to submit one notification.

How Do I Submit My R&D Notification Form?

 

Step 1: Find the Notification Form on HMRC’s Website

The notification form can be found on the government web pages.

Make sure you have your Government Gateway login ready. If you don’t have one, you’ll need to register before accessing the form.

Step 2: Fill Out the Claim Notification Form

The key sections include:

1. Your Company Unique Taxpayer Reference (UTR) – This is the same UTR you use for your Company Tax Return
2. Main Contact Details – Your main senior internal R&D contact for your company who is responsible for your claim
3. Agent Contact Details – Every person who has advised your claim, analysed costs, created technical assessments, given information or completed your online forms or tax return
4. Your Accounting Period – The start and end dates of your company’s accounting period as laid out in your tax return
5. Your Period of Account Start and end Dates – This could be the same or different to your accounting period
6. Your Planned R&D Activities – Detail the number of research and development projects, and how this work meets the definition of R&D. You don’t need to include evidence at this stage

Step 3: Submitting Online

Once complete and authorised, the form must be submitted electronically via HMRC’s secure portal.

Digital Acknowledgement from HMRC

After submission, HMRC will issue a digital receipt confirming that your notification has been received. Keep this acknowledgement for your records.

What Happens After Submission?

Once your claim notification form has been submitted, HMRC will initiate a review process to verify compliance with the R&D tax relief criteria:

• Notification Verification –  HMRC checks the accuracy of the submitted information
• Initial Review – Preliminary assessment to ensure all required details are provided
• Further Enquiry – HMRC may request additional documentation or clarification
• Outcome Communication – Notification of approval, denial, or need for further information

Download our handy R&D Tax Credit Guide to find more tips and tricks for maximising your entitlement.

What Happens if I Make a Mistake on My CNF?

If you make a mistake on your advance notification form for R&D, HMRC may reject your R&D claim or request further clarification.

Errors can’t always be corrected later, so getting expert help early is the safest route to compliance.

Can I Appeal if My CNF is Rejected?

If your pre-notification form for R&D is rejected, there’s no formal appeal process—accurate resubmission within the deadline is your only option.

What are the Benefits of Early Notification?

By informing HMRC early, you can streamline your R&D claim process and mitigate potential delays.

The Benefits	How This Can Boost Your Claim
Early Planning	You have more time for structured documentation and compliance
Tax Benefits	Your business maximises its potential tax relief opportunities
Filling Out Your Form	You have all of your ducks in a row when it comes to claiming
Strategic Advantages	You get a competitive edge in financial planning and resource allocation

 

What are the Risks of Claiming Without Notifying HMRC?

Failing to notify HMRC about your intention to claim R&D tax relief can have serious consequences. 

Potential Consequences

Submitting a claim without proper notification could result in:

• Your claim being automatically rejected
• Significant processing delays
• Increased scrutiny of your entire tax return

Increased HMRC Scrutiny

HMRC is actively cracking down on incorrect and non-compliant claims. 

If you bypass the notification requirement, your claim may trigger a deeper investigation, which can include:

• A full enquiry into your R&D activities and accounting practices
• Requests for extensive supporting documentation
• Review of prior year claims

This scrutiny can damage your company’s reputation and slow down other dealings with HMRC.

Claim Rejection or Delay

Without a valid notification, HMRC may:

• Reject your claim outright, regardless of eligibility
• Return the claim for correction, adding weeks or months to the process
• Freeze any tax credit payments until compliance is resolved

This can disrupt your cash flow and financial planning, especially if you were relying on the R&D credit to reinvest in innovation.

Penalties and Legal Implications

Non-compliance could also lead to financial penalties, particularly if HMRC views the omission as careless or deliberate. These may include:

• Loss of entitlement to R&D relief for that period
• Interest charges on any underpaid tax
• Penalties of up to 100% of the tax benefit claimed in serious cases

In extreme instances, persistent or fraudulent non-compliance can lead to legal proceedings.

Elevate Your Claim With Alexander Clifford

For more information about the notification process and how to navigate your R&D claim, contact one of our experts.

R&D Claim Notification FAQs

Can I Amend a Notification Once Submitted?

Once a notification has been submitted, you usually cannot edit it. 

However, if you’ve made a genuine mistake or need to clarify key details, contact HMRC or your tax advisor as soon as possible. 

What if I Miss the Notification Deadline?

If you were required by HMRC to submit a CNF and you missed the deadline, this means you generally can’t claim R&D tax relief for that period of account.

Does Notification Guarantee Claim Approval?

No, your actual claim still needs to meet all eligibility criteria and be supported with detailed technical and financial evidence.

Do I Need a Specialist to Handle Notification?

While you can submit the notification yourself, working with an R&D tax specialist ensures it’s done accurately and on time. 

Mistakes at this stage can lead to delays or rejections, so expert guidance is highly recommended—especially for first-time claimants.

What are Common CNF Mistakes to Avoid?

Incorrect or incomplete forms are the most common reasons for delays in R&D claim notifications. 

Avoid using an unauthorised person, missing or unsigned declarations, and filing incorrect company details.