Claim Notification Form Deadline Checker (R&D Tax Relief)
Enter your accounting period end date to find your CNF deadline, check whether the exemption applies, and see how many days you have left. HMRC CIRD183000. Updated 2026.
The Claim Notification Form (CNF) is a mandatory pre-notification that HMRC requires before most R&D tax relief claims. It must be submitted within 6 months of the end of the accounting period for which you intend to claim. CNF applies to accounting periods beginning on or after 1 April 2023; this is separate from the merged scheme which started 1 April 2024. There is an exemption for companies that have already claimed in one of the previous three accounting periods. Miss the deadline and the claim is invalid. This tool calculates your deadline and tells you whether the exemption likely applies.
What the Claim Notification Form is and why it matters
The CNF was introduced as part of HMRC's wider R&D compliance reform. Before 2023, companies could amend their Corporation Tax return to include an R&D claim without any prior notification. HMRC found that a large proportion of claims were submitted late, incorrectly, or by companies with no genuine qualifying activity. The CNF is a gatekeeping step that gives HMRC advance notice of who intends to claim.
The requirement is set out at HMRC CIRD183000. It is a statutory requirement under Finance (No.2) Act 2023.
The 6-month deadline
The CNF must reach HMRC within 6 months of the last day of the accounting period for which relief is claimed. There is no flexibility. An accounting period ending 31 December 2024 requires a CNF by 30 June 2025. An accounting period ending 31 March 2025 requires a CNF by 30 September 2025. The deadline is calculated from the accounting period end date, not from the CT return filing date.
The 6-month window sounds generous, but in practice it runs concurrently with year-end accounting work. Many companies miss it simply because their accountant is not aware of the separate CNF obligation or the timeline is not tracked. Set a calendar reminder the day accounts are signed off.
The exemption for established claimants
Companies that have already made a qualifying R&D claim in one of the three immediately preceding accounting periods do not need to submit a CNF. The exemption recognises that HMRC already has a relationship with these claimants. The three-period window is rolling: if you claimed for the period ending March 2023, the exemption covers March 2024, March 2025, and March 2026. If you then skip a year, the March 2027 period would require a CNF again (because March 2024 is no longer within the three-period lookback).
The exemption is based on when the claim was submitted, not when the period ended. A late submission of a claim for an earlier period does not retrospectively establish the exemption for a later period where the deadline has already passed.
What the CNF asks for
The CNF is a short form submitted via HMRC's Government Gateway. It asks for:
- The company's Unique Taxpayer Reference (UTR)
- The accounting period start and end dates
- A brief description of the R&D activities planned to be claimed
- An estimate of qualifying expenditure
- Whether the claim will be under the merged scheme or ERIS
The CNF is not the same as the Additional Information Form (AIF). The AIF is the detailed technical submission that accompanies the actual claim. The CNF is the brief advance notice. Both are mandatory (subject to the CNF exemption).
Consequences of missing the deadline
If the CNF deadline passes and no CNF has been submitted (and no exemption applies), the R&D tax relief claim for that period is invalid. HMRC will reject it. There is no late submission procedure, no penalty waiver, and no tribunal route to recover the position. The claim is lost for that period.
This is a hard stop. Unlike the CT return filing deadline, which carries a penalty regime but allows late filing, the CNF deadline is a qualifying condition for the relief itself. HMRC made this clear in its guidance and in communications to agents during the 2023 consultation period.
How the CNF interacts with the AIF
The CNF and the AIF are two separate mandatory steps. The CNF comes first, within 6 months of the accounting period end. The AIF comes with the amended CT return, which must be filed within 12 months of the CT return filing deadline. For a company with a 31 March year-end, the CT return is due by 31 March of the following year, and the AIF deadline is 31 March the year after that. So the CNF must be filed by 30 September, but the AIF and actual claim can follow up to 24 months later.
A company should not wait for the AIF to be prepared before submitting the CNF. The CNF is filed on estimated figures and a brief description. It does not commit the company to the final claim quantum. Use the AIF pre-flight checklist to prepare the AIF itself when the time comes.
Timing your R&D work with your advisers
The practical implication of the CNF regime is that you need to identify your intention to claim R&D relief within 6 months of year-end. This means having at least a preliminary conversation with a specialist before that window closes. If you engage an adviser late in the process, they may be able to help with the AIF and CT return but be powerless to recover a missed CNF.
Use the R&D eligibility checker to get an indicative sense of whether a claim is worthwhile, then contact a specialist before the 6-month CNF window closes. For an overview of what qualifies, read the qualifying expenditure guide.
Common questions about the CNF
The CNF must be submitted to HMRC within 6 months of the end of the accounting period for which R&D tax relief is being claimed. For example, if your accounting period ended 31 March 2025, the CNF deadline is 30 September 2025. See HMRC CIRD183000.
Most companies making an R&D tax relief claim must submit a CNF. There is an exemption for companies that have made a qualifying R&D claim in any of the three immediately preceding accounting periods. If you have never claimed, or your last claim was more than three periods ago, you must submit a CNF.
If you miss the CNF deadline and the exemption does not apply, your R&D tax relief claim for that period is invalid. HMRC will not accept a late CNF. The claim is lost for that period. There is no appeal process for a missed CNF deadline.
No. First-time claimants must submit a CNF. The exemption only applies if you have made a qualifying R&D claim in one of the three accounting periods immediately preceding the current claim period.
Yes, but they are separate submissions. The CNF must be submitted within 6 months of the accounting period end. The AIF is submitted before or alongside the amended CT return, which has a much later deadline (typically 24 months after the accounting period end). Do not confuse the two deadlines.
HMRC's CNF asks for the company's UTR, the accounting period start and end dates, a brief description of the R&D activities, the approximate qualifying expenditure, and whether the company is claiming under the merged scheme or ERIS. It is a brief form and does not require the full technical detail of the AIF.
Approaching your CNF deadline?
If your 6-month window is closing, act now. A specialist can submit the CNF on your behalf and start preparing the AIF and CT return claim in parallel.
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