Quick answer: Yes. Nothing in HMRC's rules limits a company to one adviser, and getting a second review before you submit, or before you sign off on a claim someone else prepared, is common practice. HMRC does not regulate tax advisers, so checking a claim against its own published guidance on qualifying R&D is a reasonable first step.
Why would a company want a second opinion on an R&D claim?
The two most common reasons are risk and confidence. On risk: an R&D claim that does not hold up under scrutiny does not just get rejected, it can trigger a wider HMRC compliance check into the company's tax affairs. Our guide to HMRC enquiries sets out what that process generally involves. On confidence: because HMRC does not regulate tax agents, a director signing off a claim has no independent guarantee that the firm that prepared it applied HMRC's test correctly. A second opinion is a way of closing that gap before HMRC does.
What does HMRC actually check when it looks at a claim?
HMRC's own guidance is specific about what counts. A qualifying project "must seek an advance in a field of science or technology" by resolving a genuine "scientific or technological uncertainty," and HMRC defines that uncertainty as existing "when an expert on the subject cannot say if something is technologically possible, or how it can be done, even after referring to all available evidence" (see Check if you can claim Research and Development tax relief). A second opinion, in practice, is mostly a check of whether the technical narrative in the claim actually meets that test, project by project, rather than describing routine engineering or normal software work dressed up as innovation. Our eligible expenses guide covers the cost side of the same question.
Does anyone have to be qualified to call themselves a tax adviser?
No, and this is the part most company directors do not expect. HMRC states outright that "anyone can call themselves a tax agent... they do not have to have qualifications or professional training and HMRC does not regulate agents" (see How to choose a tax agent). HMRC does publish a Standard for Agents setting out the conduct it expects, including being straightforward and honest and responding promptly to information requests, but meeting that standard is not verified before an adviser takes on clients. That is precisely the gap a second, independent read of a claim is designed to close.
What can a second opinion actually check, and what can it not?
A second opinion can check the technical narrative against HMRC's published eligibility test, check that costs claimed fall inside HMRC's qualifying categories, and flag anything that reads as routine work rather than genuine technological uncertainty. It is not the same as HMRC's own Advance Assurance service, which some first-time SME claimants can apply for directly from HMRC, with a newer targeted pilot for specific high-risk claim areas running until May 2027. Advance Assurance is HMRC agreeing in advance to accept a claim it has not yet seen in full; a second opinion is an independent adviser reviewing a claim that already exists.
What if the first claim has already been submitted and might be wrong?
If the normal amendment window for the Company Tax Return is still open, correcting it is straightforward: amend the return directly. If that window has closed, HMRC has a specific disclosure route for R&D claims that turn out to have been overclaimed, covering how to calculate the amount owed, how to submit supporting evidence and how payment is arranged (see Tell HMRC if you've claimed too much R&D tax relief). That same guidance also explains that deliberate overclaims are handled under a different process, the Contractual Disclosure Facility, so it is worth establishing early which route actually applies.