How Long Does an HMRC R&D Tax Enquiry Take?

For UK businesses claiming R&D tax relief, receiving an HMRC R&D enquiry can be concerning. One of the most common questions businesses ask is: how long does the enquiry process take? The duration of an HMRC R&D tax enquiry varies depending on several factors, including the complexity of the claim, the level of detail provided, and HMRC’s current workload.

In this article, we’ll break down the key stages of an HMRC R&D enquiry, the factors that affect its length, and how businesses can speed up the process.

What Triggers an HMRC R&D Enquiry?

Before discussing timeframes, it’s essential to understand why an enquiry may be opened. HMRC typically investigates R&D tax credit claims when:

There are inconsistencies or errors in the claim submission.
The claim appears overstated or lacks sufficient evidence.
The business is making a first-time claim.
The company’s R&D expenditure has increased significantly compared to previous claims.
HMRC is conducting random compliance checks.

The Stages of an HMRC R&D Enquiry & Estimated Timelines

A typical HMRC R&D enquiry follows these key stages:

1. Initial Enquiry Notification (1-2 Weeks)

HMRC will notify the claimant (or their agent) in writing that an enquiry has been opened.
The letter will outline the areas of concern and request further information.

✅ Tip: Businesses should respond promptly to avoid unnecessary delays.

2. Preparing and Submitting a Response (2-4 Weeks)

Businesses must gather and submit supporting evidence, including technical justifications, project details, and cost breakdowns.
HMRC typically sets a deadline of 30 days for responses.
If additional time is needed, businesses can request an extension.

✅ Tip: Ensuring the response is clear, detailed, and well-structured can prevent further questions and shorten the enquiry duration.

3. HMRC Review & Follow-Up Questions (4-12 Weeks)

Once the response is submitted, HMRC will assess the evidence.
They may request additional clarifications, schedule calls or meetings, or conduct a site visit if needed.
Some enquiries are resolved quickly, while more complex cases may take several months.

✅ Tip: Working with an R&D tax specialist can help ensure that HMRC’s concerns are addressed efficiently.

4. Enquiry Resolution & Decision (6-18 Weeks Total)

HMRC will either approve, amend, or reject the claim.
If adjustments are needed, they will issue a revised claim value and tax credit amount.
If the claim is rejected, businesses may need to appeal or negotiate further.

✅ Tip: Keeping thorough R&D records can help expedite claim approval and reduce the risk of disputes.

Factors That Affect the Length of an HMRC R&D Enquiry

The timeframe of an enquiry can vary based on:

Complexity of the Claim – Claims involving multiple projects, high-value costs, or niche technical fields may take longer to assess.
Quality of Supporting Evidence – A well-documented claim is likely to be resolved faster than one with vague justifications.
HMRC’s Workload – During peak times, HMRC may take longer to review claims.
Responsiveness of the Business – Delays in providing additional information can extend the enquiry period.
The Need for Site Visits or Interviews – If HMRC requires a more detailed review, the process can take longer.

How to Speed Up the Enquiry Process

Businesses can take proactive steps to minimise delays and ensure a smooth enquiry process:

✔️ Submit a Fully Compliant Claim – Ensure your R&D tax credit claim is accurate, well-evidenced, and aligns with HMRC’s guidelines. ✔️ Respond Quickly – Meet deadlines for providing additional information to avoid unnecessary extensions. ✔️ Work with an R&D Specialist – Professional support can help navigate HMRC enquiries efficiently and reduce processing times. ✔️ Keep Detailed Records – Comprehensive documentation of R&D activities ensures claims are backed by strong evidence, reducing the likelihood of prolonged disputes.

Final Thoughts

An HMRC R&D tax enquiry can take anywhere from 6 weeks to several months, depending on the complexity of the claim and the quality of supporting documentation. However, businesses that submit robust claims, respond promptly, and seek expert guidance can significantly reduce delays.

At R&D Enquiries, we specialise in helping businesses navigate HMRC R&D tax enquiries, ensuring compliance and maximising claim success.

👉 Contact us today for expert support in handling your R&D tax credit enquiry.