United Kingdom: If your claim is reviewed

A compliance check has deadlines, and the decision letter that ends it starts a 30 day clock. Before you reply to anything, read your engagement letter to see what help it provides, tell your adviser the same day, and take advice from someone who can see the letter and the claim. This page describes the process in general terms from HMRC's own guidance; it is not a guide to handling a check, and nothing here replaces advice on your own case.

HMRC checks a claim through a compliance check, also called an enquiry, which starts with a letter. HMRC tells you what it needs when the check starts, and may ask you to send information or documents, to attend a meeting, or to allow a visit to inspect premises, assets and records.1Source 1HMRC, Compliance checks: general information, CC/FS1a (30 April 2025). HMRC can open an enquiry into a Company Tax Return within 12 months of the day the return was delivered, and later for a late return; after that window its route is a discovery assessment within the time limits on the your responsibility page.2Source 2HMRC Enquiry Manual EM1510 (30 September 2026); HMRC Compliance Handbook CH51300 (7 October 2026).

For an R&D claim, HMRC's manual says it would normally ask the company to explain in plain language the advance in science or technology it sought, the uncertainties it faced and when they were resolved, and which activities meet the definition. The manual says the officer should gather all the facts and listen to the company before deciding.3Source 3HMRC manual CIRD80520, R&D tax relief: examining a claim: introduction (25 August 2026). HMRC's practice note says it will be sympathetic and supportive when dealing with queries and enquiries, and expects companies and their agents to be open and clear about their R&D activities in return.4Source 4HMRC manual CIRD80525, practice note (25 August 2026). HMRC's published approach to R&D reliefs also says it takes action against agents who breach its standard.5Source 5HMRC, HMRC's approach to Research and Development tax reliefs (17 July 2023).

At the end of a check HMRC sends one or more decision notices, such as an assessment, a penalty notice or a letter explaining the final position, or agrees a contract settlement. It tells you how to pay any additional tax, late payment interest and penalties.1Source 1HMRC, Compliance checks: general information, CC/FS1a (30 April 2025). Where agreement cannot be reached, HMRC's manual says the normal course is to close the enquiry, after which the company can appeal the amended assessment. It also says payable credit claims should be dealt with quickly, and that officers should keep under review whether a partial payment can be made.3Source 3HMRC manual CIRD80520, R&D tax relief: examining a claim: introduction (25 August 2026).

You usually have 30 days from the date of HMRC's decision letter to send new information, to ask for a review by an HMRC officer who was not involved, or to appeal to the independent tax tribunal. A review usually takes 45 days. An appeal to the tribunal after a review must be made within 30 days of the review result. You will usually have to pay the tax before the tribunal hears the appeal. Alternative dispute resolution is available once an appeal has been made.1Source 1HMRC, Compliance checks: general information, CC/FS1a (30 April 2025). 6Source 6GOV.UK, Disagree with a tax decision or penalty. Each of these has a deadline, and the choice between them is a matter for advice.

What your adviser must do depends on the engagement letter, which is why the review and audit support clause matters before you sign. In a compliance check, the useful things an adviser does are these.

• Produce the technical narrative and the cost workings quickly and in order.
• Help the company explain the advance and the uncertainties in its own words, with the people who did the work.
• Correct any error in the claim before HMRC finds it, using the disclosure route on the your responsibility page.
• Tell you plainly what a decision means and what your options are.

Every agent involved in the claim is named on the additional information form,7Source 7HMRC, Submit detailed information before you claim Research and Development (R&D) tax relief (26 September 2025). and HMRC can act against an agent who breaches its standard,5Source 5HMRC, HMRC's approach to Research and Development tax reliefs (17 July 2023). but none of that moves the tax, interest or penalty off the company. If the adviser's help is charged by the hour, agree an estimate and a ceiling before the work starts. The companies under review page and the claim reduced on review page cover the fee side.

• Your responsibility and complaints about an adviser in the United Kingdom
• How do you handle a tax authority review? and is review support included?
• Getting independent advice

Sources

1. HMRC, Compliance checks: general information, CC/FS1a (30 April 2025).    Back
2. HMRC Enquiry Manual EM1510 (30 September 2026); HMRC Compliance Handbook CH51300 (7 October 2026).  Back
3. HMRC manual CIRD80520, R&D tax relief: examining a claim: introduction (25 August 2026).   Back
4. HMRC manual CIRD80525, practice note (25 August 2026).  Back
5. HMRC, HMRC's approach to Research and Development tax reliefs (17 July 2023).   Back
6. GOV.UK, Disagree with a tax decision or penalty.  Back
7. HMRC, Submit detailed information before you claim Research and Development (R&D) tax relief (26 September 2025).  Back