R&D Tax Relief Claim Deadlines and Notification Requirements

Understand when to claim, which HMRC forms may be required and what's changing in 2027.

Preparing a claim involves meeting filing deadlines and procedural requirements. Missing a deadline or required submission can affect claim validity.

1. What is the R&D tax relief claim deadline?

For accounting periods beginning on or after 1 April 2023, the claim deadline generally depends on the company's period of account:

These are distinct from the ordinary Company Tax Return filing deadline. A 12-month period ending 31 December 2025 would ordinarily have an R&D claim deadline of 31 December 2027. Older periods may have different rules. A period of account containing more than one Corporation Tax accounting period may require separate claims.

2. What is the Claim Notification Form?

Under rules applying before the announced 2027 removal, a Claim Notification Form (CNF) may be necessary for companies claiming for the first time or without a relevant recent claim. Where required, the deadline is generally six months after the end of the relevant period of account. Check the exact conditions against the company's claim history and periods.

3. Important: HMRC changes announced for 2027

On 28 October 2026, HMRC published a policy paper announcing simplification measures.

Claim notification to be removed from 1 April 2027

The government announced that companies making R&D claims on or after 1 April 2027 would no longer need a Claim Notification Form, subject to necessary legislative amendments.

The relevant date is when the claim is made, not necessarily when the R&D project took place.

As of 29 October 2026, this is an announced change and must not be treated as already in force.

Additional Information Form to be simplified from autumn 2027

HMRC announced plans to simplify and rationalise the Additional Information Form (AIF) from autumn 2027. Details are pending; continue following requirements applicable when filing.

What is not being removed?

The announcement does not remove the Corporation Tax claim process, the general R&D claim deadline or the need to substantiate activities and expenditure.

4. What is the Additional Information Form?

The AIF provides HMRC with information supporting the claim. Under current requirements, it must be submitted before the Company Tax Return containing the R&D claim. It includes company details, qualifying expenditure and technical project information. Check the final autumn 2027 requirements when HMRC publishes them.

5. Claim deadline versus filing deadline

Distinguish:

• Company Tax Return deadline: Ordinary deadline for filing the Corporation Tax return.
• R&D claim deadline: Last date by which the R&D claim must be made.
• Additional form deadlines: Notification and information requirements applicable to the claim.

These dates may differ.

6. How to avoid missing a requirement

1. Confirm the period of account.
2. Identify Corporation Tax accounting period(s).
3. Calculate the R&D claim deadline.
4. Check notification requirements applicable when claiming.
5. Check AIF requirements.
6. Allow time to prepare technical evidence and costs.
7. Complete the necessary HMRC filing before the applicable deadline.

Do not assume an upcoming change removes a current obligation.

7. Can you prepare before the deadline?

Yes. Preparing technical explanations, project evidence and expenditure early can reduce last-minute work. You need not wait until the filing deadline.

Official HMRC references

• Make a claim for R&D tax relief
• Submit detailed information before claiming
• HMRC policy paper: improving the customer experience, 28 October 2026

Future changes described here are proposals unless enacted. Check the rules for the actual claim date and accounting period.