R&D Claim Notification Form: Rules and Exemptions

For accounting periods beginning on or after 1 April 2023, HMRC requires companies that have not recently claimed R&D Tax Relief to submit a Claim Notification Form before the substantive R&D claim is filed. The form is sometimes called the Advance Notification Form (ANF) or simply the pre-notification.

It is a separate document from the Additional Information Form (AIF), which every R&D claimant must file regardless of history. The Claim Notification Form sits earlier in the process and applies to a narrower group.

To help UK SMEs work out whether they need to file, we have built a free Pre-Notification calculator that walks through the test in under two minutes. With deadlines for January, February and March 2026 year-ends falling between now and the end of September, the rules below explain what the calculator is testing for and why the answer matters.

Who this applies to

The Claim Notification Form is required where:

• The company is making an R&D claim for an accounting period beginning on or after 1 April 2023, AND
• The company is a first-time claimant, or has not made a valid R&D claim in the three years ending on the last day of the notification period (a “gap claimant”).

Companies that have claimed regularly within the previous three years are generally exempt. The exceptions to that exemption are covered below.

The claim notification period: when the clock runs

The notification period begins on the first day of the period of account and ends six months after the end of the period of account. For a company with a 31 March year-end and a 12-month accounting period, the notification period for the 2025-26 accounting period runs from 1 April 2025 to 30 September 2026.

The form is filed online through HMRC’s Tell HMRC you want to claim R&D tax relief service. It can be submitted by the company or by an agent acting on its behalf.

The information required on the form is limited: company UTR, agent details where one is used, named contacts at the company, the accounting period to which the claim relates, and a high-level summary of the R&D project. It is not a substantive technical narrative. The AIF carries that work.

Imminent deadlines: are you up against the clock?

For first-time and gap claimants with year-ends in early 2026, the Claim Notification Form deadlines fall over the next three months. The three most common UK year-end dates produce three concrete deadlines:

• 31 January 2026 year-end: Claim Notification Form due by 31 July 2026. That is this month.
• 28 February 2026 year-end: Claim Notification Form due by 28 August 2026.
• 31 March 2026 year-end: Claim Notification Form due by 30 September 2026. The most common UK year-end and by far the largest cluster of affected companies.

If your company has one of these year-ends and you are a first-time claimant, or you have not made a valid R&D claim in the previous three years, the form must reach HMRC by the date above. Miss the deadline and the right to claim R&D Tax Relief for that period is gone.

This is a good moment to explore your eligibility and understand whether or not it is worth submitting a Pre-Notification form to HMRC. Our free Pre-Notification calculator returns a yes or no in under two minutes for any year-end date you provide.

The 3-year exemption

A company is exempt from filing the Claim Notification Form if it has made a valid R&D claim in the three years ending on the last day of the relevant claim notification period.

For a 31 March 2026 year-end with a notification period ending 30 September 2026, the relevant 3-year window is 1 October 2023 to 30 September 2026. Any valid R&D claim submitted to HMRC during that window exempts the company from the notification requirement for the 2025-26 claim.

“Valid” matters. A claim that was withdrawn, rejected by HMRC, or never properly submitted does not count for the purpose of the exemption.

Two exceptions to the exemption (you still need to notify)

Even where a company has claimed within the previous three years, the Claim Notification Form must still be filed in two specific scenarios:

Exception 1: a previous claim was rejected by HMRC

Where HMRC rejected the company’s R&D claim by removing the R&D figures from the Company Tax Return (typically as the outcome of an enquiry), that claim is not “valid” for the purposes of the exemption. The company falls back into the notification requirement for any subsequent claim.

Exception 2: a pre-April 2023 amendment received on or after 1 April 2023

Where the company’s only recent claim was made by amending a Company Tax Return for an accounting period beginning before 1 April 2023, and the amendment was received by HMRC on or after 1 April 2023, that amendment does not count towards the exemption. The company must still file a Claim Notification Form for any accounting period beginning on or after 1 April 2023.

This second exception caught several companies during 2024 and 2025 that believed a recent amendment to an older period would carry them through. It does not.

Claim Notification Form vs Additional Information Form: a quick comparison

The two forms are routinely confused. Both are mandatory for companies that need them. They are not interchangeable.

Issue	Claim Notification Form	Additional Information Form (AIF)
Who must file	First-time and gap claimants only	Every R&D claimant
In force from	Accounting periods beginning on or after 1 April 2023	All claims submitted on or after 8 August 2023
Deadline	Within 6 months after the end of the accounting period	Before the Company Tax Return containing the R&D claim is filed
Information required	Light: company UTR, contacts, project summary	Substantive: project descriptions against DSIT R&D guidelines, qualifying costs by category, named senior officer
Submitted via	gov.uk service	gov.uk service
Effect of missing the deadline	Claim is invalid for that accounting period	Claim is invalid; HMRC removes R&D figures from the CT600

Worked example

A UK manufacturing company has a 31 March 2026 year-end. The company has never claimed R&D Tax Relief before.

• Accounting period: 1 April 2025 to 31 March 2026.
• Period of account: same.
• Claim notification period: 1 April 2025 to 30 September 2026.
• Deadline to file the Claim Notification Form: 30 September 2026.
• AIF deadline: before the CT600 is filed (CT600 itself due by 31 March 2027).

If the company files the Claim Notification Form on or before 30 September 2026 and the AIF before the CT600, the claim can proceed in the normal way. If the Claim Notification Form is not filed by 30 September 2026, HMRC will treat the R&D claim as invalid, with no retrospective remedy.

How to check whether you need to notify

The test is straightforward in principle and easy to get wrong in practice. Three factors interact: the dates of any previous R&D claim, the dates of the current accounting period, and the validity of the previous claim (taking the two exceptions above into account).

Our free Pre-Notification calculator runs the test on the dates you provide. It asks for the current accounting period and the date of the company’s most recent R&D claim (if any), and returns a yes or no answer on whether a Claim Notification Form is required, with the notification deadline if it is. The calculator is free to use, requires no sign-up, and stores no company data.

For companies whose previous claim was amended, rejected or marginally inside the three-year window, the calculator surfaces the right question and the right deadline rather than leaving the company to interpret the rule cold.

What happens if you miss the deadline

The consequence is binary. A Claim Notification Form filed after the end of the notification period is out of time, and the R&D claim for that accounting period is invalid. HMRC will remove the R&D figures from the Company Tax Return.

There is no statutory mechanism to make a late notification good. The company cannot rectify the position by filing later, by paying a penalty, or by appealing to HMRC’s discretion. The relief for that accounting period is lost.

The only routes that remain are to claim for the next accounting period (subject to the same notification test) and, separately, to consider whether anything else in the company’s affairs justifies an HMRC challenge against the rejection. Neither restores the lost claim.

Lexmore’s View

The Claim Notification Form is a low-information, high-consequence filing. The information HMRC requires is minimal. The cost of missing the deadline is the full value of the R&D claim for that period.

For first-time claimants, the form is straightforward provided the deadline is in the diary. For companies who have claimed before but whose claim history is broken (a gap year, an amendment, a rejected claim, a sale or restructure), the right answer on whether notification is required is rarely obvious and frequently wrong.

We built the Pre-Notification calculator because the question is asked often, the rule is technical, and the consequences of getting it wrong are out of proportion to the difficulty of the test. It is free, takes under two minutes, and produces a clear written answer for the period the company is asking about.

Clear deadline. Clear evidence. Clear claim.

References

• Tell HMRC you want to claim Research and Development (R&D) tax relief | gov.uk
• Submit detailed information before you claim R&D tax relief (Additional Information Form) | gov.uk
• Research and Development (R&D) tax relief: the merged scheme and enhanced R&D intensive support | gov.uk
• HMRC Corporate Intangibles Research and Development Manual (CIRD)
• Lexmore Pre-Notification calculator