HMRC R&D claim processing times and reviews

Processing time vs review: what’s the difference?

When people ask “how long will HMRC take?”, they usually mean one of two things:

Processing is HMRC updating your Corporation Tax position based on your CT600 and R&D entries and where relevant, issuing a repayment or credit.

Review is HMRC deciding they need more comfort on the eligibility story, the costs, or the validity of the submission. A review can be light touch, or it can become a formal compliance check (also know as an enquiry). HMRC’s published compliance approach makes clear that they use risk assessment and compliance activity to tackle error and fraud, which is one reason timeframes have become less predictable.  

What happens after you submit an R&D claim

For accounting periods beginning on or after 1 April 2024, most companies claim through the merged R&D tax relief scheme, with ERIS available for some R&D intensive loss-making SMEs. The claim is still made through your Company Tax Return and supporting process steps.  

In practical terms, HMRC will typically:

1. Receive your CT600 and compute the Corporation Tax position
2. Use the information you have submitted to risk assess the claim
3. Either process the outcome or ask questions where something looks unclear, inconsistent, or high-risk
   

The process steps that can affect speed

Additional Information Form (AIF)

For most claims, you must submit an AIF before you claim. Missing the AIF can invalidate the claim, and incomplete or inconsistent AIF content increases the chance of follow-up questions.  

Claim Notification Form (CNF) for some businesses

If you are a first-time or infrequent claimant, you may need to submit a CNF within the required window. If claim notification applies and you miss it, the claim can be invalid even if you are otherwise in time to amend the CT600.

Why HMRC might take longer than you expect

Delays are usually caused by one or more of these:

• Risk flags: claims that look unusual for the sector, spike year-on-year, or have weak technical explanations
• Evidence gaps: costs that do not reconcile to payroll and the ledger, or staff time logic that is not explained
• Complex cost areas: subcontractors, EPWs, and apportionment, especially where contract wording and “who bears the risk” is not clear
• Process issues: AIF submitted late, missing details, CNF missed where required, or a mismatch between the CT600 entries and the AIF
• General HMRC capacity: even non-R&D repayments can be impacted by wider operational backlogs at times
  

Payment is not the same as acceptance

Even if a repayment is made, HMRC can still open a compliance check within the normal enquiry window. For Corporation Tax, HMRC’s manuals set out that where a return is delivered on or before the filing date, notice of enquiry can generally be given within 12 months (with nuances for different group situations and late returns).  

What you can do to reduce delays

A fast outcome usually comes from making the reviewer’s job easy. The highest impact actions are:

• Submit the AIF early and keep it consistent with the technical report and cost schedules
• Reconcile your totals from claim schedules to payroll, pensions, NIC, and the trial balance before filing
• Keep the technical story specific: uncertainty, baseline, attempted resolution, and why it was not readily deducible
• Use plain-English apportionment logic for staff time and third-party costs, with a short evidence trail
• Check repayment setup: if you expect a Corporation Tax repayment, make sure the Company Tax Return includes the repayment request details and payment method
  

If you need a repayment quickly

There is no guaranteed “fast track”, but you can reduce friction by filing outside peak periods where possible, ensuring the AIF is complete, and avoiding the most common inconsistency errors. If cash timing is critical, plan the claim prep earlier in the year so you are not rushing the evidence at filing time