HMRC R&D Enquiry Timeline: Week-by-Week (What Happens When)

An HMRC R&D enquiry under the merged scheme, ERIS, or legacy SME/RDEC scheme follows a process governed by the Taxes Management Act 1970 and Schedule 36 of the Finance Act 2008. HMRC's powers to open enquiries and request information are set out in published guidance at gov.uk. This page maps the typical sequence for a standard compliance check. Use the eligibility checker to review your claim position. For the enquiry types covered by this timeline, see the HMRC enquiries pillar page.

Overview: Four Phases

An HMRC R&D enquiry moves through four phases. The total elapsed time from opening to closure ranges from 3 months (simple compliance check, single information exchange) to 36 months or more (contested full enquiry with meetings and amendment). The phases are:

• Phase 1: Opening (weeks 1 to 4). HMRC issues an opening letter or information notice. The company acknowledges receipt and assembles its response team.
• Phase 2: Information exchange (weeks 4 to 26). HMRC asks questions; the company responds; HMRC asks follow-up questions. This phase can have one to five rounds, depending on the complexity of the claim and HMRC's concerns.
• Phase 3: Resolution or escalation (weeks 16 to 52+). HMRC either accepts the claim, agrees a partial amendment, or issues a formal amendment notice. Where the company disputes HMRC's position, the case moves into the appeal process.
• Phase 4: Appeal (months 9 to 36+). HMRC statutory review (up to 45 days), then First-tier Tribunal if still unresolved.

Phase 1: Opening the Enquiry (Weeks 1 to 4)

Week 1: The Opening Letter Arrives

HMRC's opening letter for an R&D compliance check is issued under section 9A of the Taxes Management Act 1970. It states that HMRC is opening an enquiry into the company's CT600 for a specified accounting period, and sets out the initial questions or requests. The letter will usually identify a named HMRC compliance officer and include a telephone number and address for correspondence.

The letter may arrive by post or, increasingly, via HMRC's online correspondence facility for those with a Government Gateway account. The date on the letter is the date HMRC treats as the opening date for statutory purposes. The 30-day response clock for initial information requests runs from the date of the letter.

Week 1 to 2: First Actions

On receipt of the opening letter, the company or its adviser should:

• Acknowledge receipt in writing within 5 to 7 days. This is not a statutory requirement but is good practice and establishes communication.
• Identify the claim period and locate the original claim working papers, Additional Information Form submission, CT600, and any correspondence with the original claim preparer.
• Assess whether the company has a specialist adviser who can handle the enquiry, or whether one needs to be engaged. If a new adviser is being brought in, notify HMRC of the representation immediately so future correspondence goes to the right person.
• Review the opening letter carefully to identify whether it is a compliance check (formal, with specific information requests) or a nudge letter (pre-enquiry, non-mandatory). If you are unsure, see the nudge letter playbook.

Weeks 2 to 4: Preparing the Initial Response

The initial response to HMRC's information requests is the most important document in the enquiry. A well-prepared response addresses every point raised, provides the requested documents in a clear and well-organised format, and does not volunteer information that HMRC has not asked for.

The typical initial information request covers: technical narrative for each qualifying project, staff time records and apportionment methodology, payroll reconciliation, and subcontractor or EPW contracts. For a full list, see the HMRC enquiries guide.

If the 30-day deadline cannot be met, write to HMRC before the deadline passes to request an extension. Most HMRC officers will grant 2 to 4 additional weeks if the reason is clearly stated. Do not allow the deadline to pass without communication; unexplained non-responses can lead to HMRC issuing a protective assessment.

Phase 2: Information Exchange (Weeks 4 to 26)

Weeks 4 to 6: Submitting the Initial Response

The initial response package should be submitted with a covering letter that sets out the structure of the documents provided, cross-references each document to the specific question or request in HMRC's letter, and flags any areas where information is partially available or where the adviser is seeking clarification of HMRC's specific concern.

Send the response to the named compliance officer at the address in the opening letter. If submitting by post, use recorded delivery and retain proof of posting. If submitting digitally via the HMRC case system, retain screen confirmation.

Weeks 6 to 14: HMRC Reviews the Response

After receiving the initial response, HMRC takes time to review the documents. There is no published service standard for how long HMRC should take to review an initial response and issue a follow-up question. In practice, the turnaround is typically 4 to 10 weeks. Some cases where HMRC has a large backlog take longer.

During this period, the company and its adviser should not contact HMRC unless there is a material change in circumstances or a clear error in the documents submitted. Unprompted contact can extend the review time rather than accelerating it.

Weeks 10 to 20: Follow-Up Questions

HMRC typically issues one to three rounds of follow-up questions in a standard R&D compliance check. Each round gives the company 30 days to respond, with extensions available on request. The questions become more focused as HMRC narrows its concerns. Common follow-up themes include:

• Requests for more technical detail on specific projects, particularly where the initial narrative did not clearly identify the scientific or technological uncertainty.
• Requests for additional payroll or time records to verify apportionment percentages claimed for specific individuals.
• Requests for evidence of the competent professional assessment at project start.
• Challenges to specific cost items, such as subcontractor costs for overseas providers or cloud costs that HMRC believes relate to production rather than R&D.

Each response should be reviewed by the specialist adviser before submission. Inconsistencies between rounds give HMRC grounds to question the reliability of the evidence.

Weeks 12 to 24: Possible Meeting with HMRC

HMRC may request a meeting where technical questions have not been resolved through the written exchange. Meetings are more common in full enquiries than in standard compliance checks. They are not compulsory; the company is entitled to conduct the entire process in writing. However, where HMRC has specific technical questions that a qualified engineer or scientist could answer more efficiently in person, a meeting can accelerate resolution.

If a meeting takes place, the company's specialist adviser should be present throughout. Technical witnesses (e.g. the lead engineer on a qualifying project) should be briefed in advance on the specific points HMRC has raised. After the meeting, the adviser should send a written summary of what was agreed or discussed to create a record.

Phase 3: Resolution or Escalation (Weeks 16 to 52+)

Resolution by Closure Notice

If HMRC is satisfied with the evidence provided, it will issue a closure notice under section 28A of the Taxes Management Act 1970. The closure notice states that the enquiry is complete and sets out whether HMRC has made any amendment to the return. If HMRC accepts the claim in full, the closure notice confirms that no amendment is required.

Once a closure notice is issued, the enquiry is formally closed. HMRC cannot reopen the same enquiry, though it can open a new enquiry into a different period or a different part of the same return that was not covered by the original enquiry.

Escalation by Amendment Notice

If HMRC disagrees with the company's position, it issues an amendment notice alongside or instead of the closure notice. The amendment notice sets out the change HMRC intends to make to the return and the basis for the change. The company has 30 days to accept the amendment or appeal it.

Accepting the amendment means paying the additional tax (and interest from the original due date, charged under section 87 of the Taxes Management Act 1970 at the rate published by HMRC). Appealing the amendment moves the case into Phase 4. For the decision framework on whether to appeal or settle, see the when-to-appeal guide.

Interest and Penalties

Where an enquiry results in an amendment to reduce the amount of R&D relief, the company will typically owe interest on the underpaid tax from the original due date. Late payment interest is charged at the rate set by HMRC under section 178 of the Finance Act 1989 and published at gov.uk.

Penalties under Schedule 24 of the Finance Act 2007 may also apply if HMRC determines that the inaccuracy in the original return was careless or deliberate. The penalty range is 0% to 100% of the potential lost revenue, subject to mitigation for prompted or unprompted disclosure and quality of cooperation. First-time offences with genuine errors and good cooperation typically attract penalties at the lower end of the range or nil penalties.

Phase 4: The Appeal Process (Months 9 to 36+)

HMRC Statutory Review

Before going to tribunal, the company can request a statutory review of HMRC's decision under section 49A of the Taxes Management Act 1970. The review is carried out by an HMRC officer who was not involved in the original enquiry. HMRC has 45 days to complete the review, though extensions are common in complex cases. The reviewing officer can uphold, vary, or cancel the amendment.

The statutory review is free and does not prevent the company from subsequently appealing to the First-tier Tribunal if unsatisfied. Many cases settle at the review stage when the reviewing officer takes a different view from the original compliance officer.

First-tier Tribunal (Tax Chamber)

If the statutory review does not resolve the dispute, the company can appeal to the First-tier Tribunal. The notice of appeal must be lodged with the Tribunal within 30 days of the statutory review conclusion letter, or within 30 days of the amendment notice if no review was requested. Cases are managed by the Tax Chamber of the First-tier Tribunal under the Tribunal Procedure (First-tier Tribunal) (Tax Chamber) Rules 2009.

Tribunal cases typically take 12 to 24 months from the appeal notice to a hearing. HMRC is required to provide its statement of case within 60 days of the notice of appeal. The company then has 42 days to provide its reply. Case management directions then set the timetable for expert evidence, witness statements, and the hearing itself.

Tribunal fees for tax cases are set by the Tribunal Procedure Committee. As of 2026, standard-track appeals (most R&D cases) do not carry issue fees, though a hearing fee may apply at the discretion of the Tribunal. The principal cost of a tribunal appeal is the professional fees of the specialist adviser and, where expert technical evidence is required, an independent expert witness.

For the case law that shapes tribunal outcomes in R&D cases, see the tribunal case law guide.

Settlement During Appeal

A large proportion of R&D cases settle before a tribunal hearing, often after the exchange of statements of case has clarified each party's position. Settlement can be reached at any point in the appeal process. A well-documented claim with strong technical evidence frequently achieves a better outcome in settlement negotiations than the original amendment notice would suggest. The when-to-appeal guide covers the negotiation dynamics in more detail.