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HMRC now apply significantly greater scrutiny to Research & Development (R&D) tax relief (formerly known as credits) claims than ever before. Businesses submitting R&D claims can expect them to be subject to risk profiling, keyword analysis, and in some cases, detailed compliance checks.
Understanding how HMRC processes R&D claims is essential for reducing delays, avoiding rejections, and ensuring full compliance with current legislation.
In this guide, we explain the complete HMRC R&D claim process, including Additional Information Forms (AIFs), HMRC compliance checks, claim approvals, and the importance of using a compliant R&D tax adviser.
HMRC process R&D tax relief claims by reviewing the Additional Information Form (AIF), validating submission requirements, conducting risk assessment checks, and potentially opening compliance enquiries before approving, adjusting, or rejecting the claim.
Even in cases where HMRC have processed an R&D claim and the company has received their benefit, HMRC can, and do, still open a compliance check later. With the normal window for a compliance check being 12 months from the date the claim was submitted, even if the claim has been processed and paid out.
The process is designed to ensure that businesses receive relief only for genuine qualifying Research & Development activities that meet UK tax legislation requirements.
The R&D claim process begins with preparing the claim itself.
This involves identifying qualifying projects, calculating eligible expenditure, and compiling the technical evidence needed to support the submission.
A compliant R&D tax claim should include:
The quality of the initial submission is extremely important. HMRC are increasingly focused on identifying poorly prepared, speculative, or unsupported claims.
Whereas businesses that rely on experienced and compliant R&D tax advisors are often in a stronger position, with claims prepared with both technical accuracy and HMRC compliance requirements in mind.
Read more information about what R&D tax credits are to determine whether your activities might qualify for a claim.
Before most R&D tax claims can be processed, HMRC requires companies to submit an Additional Information Form (AIF).
The AIF provides HMRC with detailed information about theclaim, including:
The AIF forms a key part of HMRC’s compliance process.
If the Additional Information Form is not submitted correctly, the claim may be rejected automatically.
Ensuring consistency between the AIF, technical report, and Corporation Tax Return is critical.
Once the Additional Information Form has been submitted, the business files its Corporation Tax Return (CT600), including the R&D tax relief claim.
At this stage, HMRC begin their internal review and assessment procedures.
The claim enters HMRC’s processing system where both administrative and compliance checks are carried out.
The first stage of HMRC’s review process involves validatingwhether the claim satisfies all mandatory submission requirements.
HMRC will verify that a valid AIF has been submitted.
If no valid AIF exists, the claim may be rejected before any technical review takes place.
Companies making a claim for the first time or claiming infrequently are required to submit a pre-notification form before making an R&D tax relief claim.
HMRC will check:
Failure to comply with pre-notification requirements can invalidate the claim entirely.
An experienced R&D adviser will ensure these procedural requirements and deadlines are handled correctly.
Once the administrative checks are complete, HMRC useinternal risk assessment systems to determine whether the claim requires further scrutiny.
This stage is often referred to as the claim filteringprocess.
HMRC may assess factors such as:
Claims considered low-risk may progress through the system more quickly.
Claims identified for further review may proceed to an enquiry or compliance check.
Because HMRC are focusing heavily on compliance standards, businesses should ensure their claims are properly evidenced and technically robust from the outset.
Since HMRC increased their compliance activities in relation to claims for R&D tax relief in 2021/2022, the way in which R&D claims are prepared and then processed has changed dramatically.
The most noticeable change is the introduction of the Additional Information Form (AIF) in 2023, which is now a mandatory requirement and must be completed prior to the claiming companies tax return being submitted to HMRC.
Forcing companies to provide information about R&D claims in a standardised format has allowed HMRC to vastly increase their pre-processing screening of claims, and as a result the number of R&D claims HMRC open an enquiry (aka a compliance check) into increased from 1% of all R&D claims to 20% by the start of 2025.
This 1900% increase has forced R&D advisors to undertake a much more rigorous approach to R&D claim preparation for clients, and many will find their advisor asking for lots more information than they may have done previously, increasing the admin overhead for both the claiming company and their advisor.
If HMRC require additional clarification, they may open a formal enquiry into the claim, also known as a compliance check.
An enquiry does not necessarily mean the claim is invalid. Many legitimate claims are selected for review as part of HMRC’s wider compliance activity.
However, claims lacking sufficient technical detail orsupporting evidence are more likely to encounter challenges.
HMRC may request:
The enquiry process can become complex, particularly where technical definitions or expenditure eligibility are disputed.
This is why many businesses choose to work with specialist R&D tax advisers experienced in managing HMRC enquiries and compliance reviews.
Once HMRC issue an enquiry letter, the company or its adviser must provide a formal response.
The response should clearly answer any questions asked by HMRC, while providing supporting evidence and technical clarification.
HMRC will assess whether the response adequately demonstrates:
Strong responses are typically:
Businesses that prepare robust claims from the beginning are often better positioned during the enquiry process.
Some claims proceed into deeper compliance reviews involving specialist HMRC inspectors.
During these reviews, HMRC may assess:
Following the review, HMRC may:
This stage highlights the importance of compliance-led claimpreparation.
Well-prepared claims supported by detailed evidence aregenerally easier to defend if challenged.
The time it takes HMRC to process an R&D tax reliefclaim can vary depending on several factors.
These include:
Claims that pass through HMRC's system without raising any concerns, are typically processed within 4-8 weeks.
However, where HMRC open a compliance check, processing times increase significantly, and some can take years to conclude.
Businesses should ensure claims are complete, accurate, and well-supported to minimise avoidable delays.
Understanding why HMRC reject R&D tax claims can helpbusinesses avoid common compliance issues.
Some of the most common reasons for rejection include:
Many rejected claims result from poor preparation rather than deliberate non-compliance.
Working with a trusted R&D tax consultancy helps businesses reduce these risks by ensuring claims are prepared in line with HMRC guidance and current legislation.
If HMRC reject a claim, businesses may still have options available.
Potential next steps include:
Professional support from a reputable adviser, can be extremely valuable when responding to disputes or defending legitimate claims, especially during ADR or when going through the tax tribunal process.
The R&D tax relief landscape has changed considerably in recent years.
HMRC are now placing far greater emphasis on:
As a result, choosing the right R&D tax adviser hasbecome increasingly important.
A compliant and experienced R&D consultancy can help businesses:
Responsible advisers focus not simply on maximising claim values, but on ensuring every claim is fully supportable and compliant.
Businesses should look for advisers who prioritise transparency, technical expertise, and long-term compliance rather than aggressive claim methodologies.
HMRC’s approach to R&D tax relief claims has evolved significantly, with increased scrutiny now forming a standard part of the process.
Businesses submitting claims should ensure they have:
A carefully prepared and fully compliant claim not only improves the likelihood of approval but also helps businesses navigate enquiries and compliance checks with greater confidence.
Working with an experienced R&D tax consultancy can provide reassurance that claims are prepared correctly, professionally supported, and aligned with HMRC’s latest compliance expectations. For more information, speak to one of our advisors.
Yes. HMRC may reject claims where eligibility requirements are not met, mandatory forms are missing, evidence is insufficient, or projects fail to qualify as Research & Development for tax purposes.
Common triggers include unusually large claims, weak technical narratives, inconsistencies within the submission, unsupported expenditure, sector risk profiling, or random compliance selection.
No. Many legitimate claims are selected for review as part of HMRC’s wider compliance activity.
The length of an enquiry can vary depending on the complexity of the claim and the information requested by HMRC.
Yes. HMRC may adjust claims by removing specific projects or expenditure categories while approving the remainder of the submission.
A compliant and experienced R&D adviser can help improve claim quality, technical accuracy, and supporting evidence, helping reduce the likelihood of avoidable compliance issues.
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