Do I Still Need a Claim Notification Form If I Claimed Two Years Ago?

The Claim Notification Form was introduced by HMRC's R&D reform measures and applies to accounting periods beginning on or after 1 April 2023. Under the merged R&D relief scheme, it is a pre-condition for making any R&D claim. Miss the deadline and the claim is inadmissible, with no remedy. The exemption for companies that have claimed previously is real, but it depends on a three-period lookback, not a simple "have you ever claimed" question.

What the Claim Notification Form Is

The CNF is an online pre-notification filed through HMRC's R&D portal. It tells HMRC that your company intends to make an R&D tax relief claim for a specified accounting period. It asks for:

• Your company's UTR and registered name.
• The start and end dates of the accounting period for which you plan to claim.
• The type of R&D relief you plan to claim (merged scheme RDEC or Enhanced R&D Intensive Support).
• A declaration that the activities meet the definition of R&D for tax purposes.

The CNF is not the claim itself. You still file the actual claim through your company tax return and submit the Additional Information Form. The CNF is a separate prior step. Failing to complete it by the deadline means the subsequent claim is invalid regardless of what the AIF and return contain.

The deadline for the CNF is the same as the company tax return deadline: 12 months after the end of the accounting period. For a period ending 31 March 2025, the CNF deadline is 31 March 2026.

The Exemption: Three-Period Lookback Explained

A company does not need to file the CNF if it has made an R&D tax relief claim in any of the three immediately preceding accounting periods. This is the exemption. The statutory language specifies "any of the three periods immediately preceding" the current period.

Here is how to apply it correctly.

The lookback is by accounting period, not by calendar year. If your company has a 30 June year-end and last claimed for the year ending 30 June 2021, and has not claimed since, then for the year ending 30 June 2025 you would be looking back at June 2022, June 2023, and June 2024. None of those periods contained a claim. The CNF exemption does not apply.

The Gap Trap: Why Two Years Ago May Not Be Enough

The question in this post's title asks about claiming two years ago. Whether that is sufficient depends on when you last claimed relative to the current period and how your accounting periods are structured.

If your accounting period is 12 months and you claimed in the period ending two years before the current period, that period is within the three-period lookback and the exemption applies. You do not need the CNF.

But consider a company that skipped a year. They claimed for the year ending 31 March 2022 but not for 2023 or 2024. For the year ending 31 March 2025, the three-period lookback covers 2022, 2023, and 2024. The 2022 claim falls within that window, so the exemption technically applies. However, if they also did not claim in 2023 or 2024 and are now trying to claim for 2025, they should still check whether any intervening non-claim has broken the continuity in a way that affects their position.

Group Companies: a Common Misunderstanding

The exemption is based on the specific company's own prior claims, not the claims of other companies in the same group. If Company A and Company B are in the same corporate group and Company A has claimed R&D relief in each of the last three periods but Company B has never claimed, Company B needs to file the CNF for its first claim. Company A's history does not transfer to Company B.

This catches group structures where a holding company or operating subsidiary takes on R&D activities that were previously carried out by a different entity. The entity making the current claim is the one whose prior claim history matters.

What Happens If You Miss the CNF Deadline

The consequence of missing the CNF deadline is straightforward and unforgiving: the R&D claim for that accounting period is inadmissible. HMRC will not process it. There is no penalty for missing the CNF because no claim can be made; the cost is the loss of the claim itself.

There is no late filing mechanism for the CNF and no HMRC discretion to accept a late notification. This is categorically different from other tax deadlines where a reasonable excuse argument might succeed. The CNF deadline is a hard gate.

If you have recently missed a CNF deadline for a period that has now closed, the only question is whether the two-year amendment window for that period is still open. If it is, and you could have filed the CNF on time but did not, the period is nonetheless closed for R&D purposes. The amendment window relates to the claim; the CNF is a pre-condition to the claim. Without the CNF, there is no claim to amend. See our post on late R&D claims for the related time limit analysis.

How to Check Whether You Need to File the CNF

1. Identify the accounting period for which you plan to claim R&D relief.
2. Identify the three immediately preceding accounting periods for that same company.
3. Check whether the company (not a group company) made an R&D tax relief claim for any of those three periods.
4. If yes to step 3, the exemption applies and you do not need the CNF for the current period.
5. If no to step 3, you must file the CNF by the company tax return deadline for the current period.

Use our eligibility checker to run through the basic qualifying criteria before you reach the CNF stage, and speak to a specialist adviser who understands the procedural requirements as well as the substantive ones. An adviser who handles the expenditure categories but does not know the CNF rules is a gap in your coverage.