The R&D Claim Notification Form
Written and reviewed by the R&D Tax Accountants editorial team. Last reviewed 8 August 2026.
For accounting periods beginning on or after 1 April 2023, some companies have to tell HMRC they intend to claim R&D relief before they claim it. The claim notification form is that step, and it has a hard deadline that sits well before the normal claim deadline.
It is the single most damaging deadline in the regime, because missing it makes the claim invalid outright. There is no reasonable excuse route and no late notification. A company with a strong claim and good records loses it entirely.
Who Has to Notify
A company has to submit a claim notification form if it is claiming for the first time, or if its last claim was made more than three years before the end date of the claim notification period.
The three-year rule is what makes this a live issue for established claimants rather than only for start-ups. A company that claimed regularly, then had two or three years without qualifying projects, can find itself treated as a new claimant again. Assuming a history of claims removes the requirement is a common and expensive mistake.
The Notification Window
The claim notification period opens on the first day of the period of account and closes six months after the end of the period of account. That is the whole window, and it runs on the period of account rather than the accounting period.
Set against the claim deadline itself, which is 24 months from the last day of the period of account where that period is 18 months or less, the notification window closes 18 months earlier. A company that discovers the relief a year and a half after its year end may still be comfortably inside the amendment window and already permanently outside the notification window. The interaction is set out further on the R&D tax credits page.
The Three-Year Lookback Exemption
A company does not need to notify if it claimed R&D relief within three years of the last date of its claim notification period. That is the exemption, and it is measured from the notification period rather than from the current year end.
There are carve-outs to check before relying on it. A claim HMRC rejected, and amendments received after 1 April 2023, do not necessarily count in the way a company might assume. Where the claim history is at all irregular, the safe course is to notify: an unnecessary notification costs nothing, and a missing one costs the whole claim.
What the Notification Asks For
The form is short. It asks for the company Unique Taxpayer Reference, the senior R&D contact at the company, contact details for every agent involved in the claim, the accounting period start and end dates, the period of account start and end dates, and a summary of the high-level planned activities.
The summary is a summary. It does not commit the company to the projects listed and it does not replace the technical narrative, which goes on the additional information form later. Companies sometimes delay notifying because they do not yet know the final shape of the claim, which gets the risk backwards: the notification is cheap and reversible, and the deadline is not.
HMRC sets out who must notify and by when in its claim notification guidance. Companies new to the relief may also want the eligibility overview published by the British Business Bank.