How to Claim R&D Tax Credits

Key facts

R&D tax credits are claimed through your Corporation Tax return (CT600).
You must also submit the mandatory HMRC Additional Information Form digitally before or at the same time as your CT600.
New claimants (or those who have not claimed for 3+ years) must pre-notify HMRC within 6 months of the end of the accounting period.
Claims must be made within 2 years of the end of the relevant accounting period.
You should prepare a technical report explaining each qualifying project, even though it is not submitted with the return.

The Claiming Process at a Glance

Claiming R&D tax credits involves several steps, from identifying your qualifying projects through to receiving the credit or reduced CT bill. Here is the end-to-end process:^[1]

Step	Action	When
1	Pre-notify HMRC (if required)	Within 6 months of period end
2	Identify qualifying R&D projects	During or after the accounting period
3	Calculate qualifying expenditure	After period end
4	Prepare the technical report	Before submitting the claim
5	Complete the Additional Information Form	Before or with CT600
6	Submit the CT600 with R&D boxes completed	Within 2 years of period end
7	HMRC processes the claim	Typically 40 working days

Step 1: Pre-Notify HMRC (If Required)

If you are a first-time R&D claimant or have not claimed R&D relief in any of your company’s last three accounting periods, you must pre-notify HMRC of your intention to claim.^[4]

Key rules for pre-notification:

Submit the notification within 6 months of the end of the accounting period for which you want to claim
Use the online notification form on GOV.UK
Provide basic details: company name, UTR, accounting period dates, and a brief description of the R&D
If you miss the 6-month deadline, you cannot claim for that period

Important: Pre-notification is not required if your company has made an R&D claim in any of the previous three accounting periods. Existing claimants can continue to claim without notifying HMRC in advance.

Step 2: Identify Qualifying R&D Projects

Review your company’s activities during the accounting period and identify projects that sought to achieve an advance in science or technology by resolving scientific or technological uncertainty.^[1]

For each project, document:

What advance in science or technology was being sought
What uncertainty existed at the outset
How the uncertainty was addressed (the systematic approach)
What the outcome was (success, failure, or ongoing)
Who worked on the project and for how long

Step 3: Calculate Qualifying Expenditure

For each qualifying project, calculate the eligible costs across all categories:^[2]

Staff costs — apportioned by time spent on R&D
Subcontractor costs — at 65% for unconnected parties
Externally provided workers — at 65% of payments
Consumable materials — consumed by the R&D process
Software and data licences — directly used in R&D
Utilities — apportioned to R&D activities

Step 4: Prepare the Technical Report

Although the technical report is not submitted with your CT600, it is essential to have one prepared before you claim. HMRC may request it during a compliance check, and having a well-written report significantly strengthens your claim.^[1]

See our dedicated guide: The R&D Technical Report.

Step 5: Complete the Additional Information Form

Since August 2023, all R&D claims must be accompanied by an Additional Information Form (AIF), submitted digitally through HMRC’s online service.^[3]

The AIF requires:

A description of each qualifying R&D project (up to a specified character limit)
The name of a “senior officer” of the company who is responsible for the claim
Details of any R&D agent or adviser used
A breakdown of qualifying expenditure by cost category

The AIF must be submitted before or at the same time as the CT600. If you submit a CT600 with an R&D claim but no AIF, the claim will be rejected.

Tip: Prepare the AIF carefully — the project descriptions are reviewed by HMRC and form a key part of their initial assessment. Write clear, specific descriptions focusing on the uncertainty and the advance, not just a general overview of the project.

Step 6: Submit the CT600

Include the R&D claim in your Corporation Tax return by completing the relevant boxes in the CT600:^[2]

Under the merged RDEC, enter the credit amount in the RDEC section of the CT600
If claiming ERIS, enter the enhanced deduction and any payable credit in the appropriate SME sections
Ensure the figures match the Additional Information Form

If you are claiming for a previous period, submit an amended CT600 for that period.

Step 7: HMRC Processing

HMRC aims to process straightforward R&D claims within 40 working days. During this time, HMRC may:^[1]

Process the claim and issue the credit (or reduce your CT liability)
Request further information informally
Open a formal enquiry under Schedule 18 Finance Act 1998

If the claim results in a payable credit (because the company is loss-making), HMRC will issue a payment once the claim is processed.

Frequently Asked Questions

Can I claim R&D tax credits myself or do I need an adviser?

You can prepare and submit an R&D claim yourself. The claim is made through your CT600 Corporation Tax return, which you or your accountant submit to HMRC. However, many companies use specialist R&D advisers because the process of identifying qualifying activities and preparing the technical report can be complex. There is no requirement to use an adviser.

How long does it take to receive the credit?

HMRC aims to process R&D claims within 40 working days if the claim is straightforward. However, HMRC has increased its compliance activity, so some claims take longer if they are selected for review. Having a well-documented technical report and clear cost calculations can speed up the process.

Can I claim for previous years?

Yes, you can claim for any accounting period where the claim deadline has not yet passed. The deadline is 2 years from the end of the accounting period. For example, for an accounting period ending 31 March 2025, you have until 31 March 2027 to claim. You submit an amended CT600 for each prior period.

What happens after I submit my claim?

HMRC may process the claim and issue the credit, or they may open an enquiry to review the claim in more detail. If the claim is straightforward and well-documented, it is typically processed within 40 working days. If HMRC opens an enquiry, they will write to you requesting further information about the qualifying activities and costs.

Sources

Corporation Tax: Research and Development (R&D) relief — GOV.UK
Claim R&D tax relief — GOV.UK
Mandatory additional information form for R&D claims — GOV.UK
Notify HMRC of R&D tax relief in advance — GOV.UK