R&D tax relief

You think a past R&D claim was wrong. What now?

A previous claim, prepared by a former adviser or even in-house, is starting to look shakier the more you look at it: costs that were probably over-included, work that might not really have cleared the bar, a narrative that reads as generous rather than accurate. This is a genuinely under-explained situation, so here is the honest, general shape of it.

Tell us what's happening R&D tax relief overview

Founded by Adam Parker No obligation to talk it through

Why this is worth taking seriously now, not later

The gap between finding it yourself and HMRC finding it

Across UK tax, not just R&D, correcting a return yourself is generally treated differently from the same error being uncovered by HMRC first. That's the reason this situation is worth acting on rather than sitting with. HMRC's own published figures show compliance-check coverage rose from 10% of claims in 2022-23 to 17% in 2023-24 (see HMRC's published approach to R&D tax reliefs, 2023 to 2024, and what an HMRC enquiry actually involves for what that means in practice), so a claim with a real weakness in it is meaningfully more likely to be looked at now than it might have been a few years ago.

Working out if there's actually a problem

Suspicion isn't the same as certainty, but it's worth resolving either way

Some of what triggers this feeling turns out, on proper review, to be within normal bounds: a judgement call on cost apportionment that was defensible even if generous, or a technical narrative that was thinner than ideal but not actually wrong. Other times the review confirms the worry: costs that shouldn't have been included, a project that genuinely didn't meet the uncertainty bar, or a narrative that overstated what actually happened. Either way, a proper review by someone who wasn't involved in preparing the original claim is the honest starting point, not guessing.

Where this most often surfaces: a change of adviser, a funding round, a sale process, or simply a new finance hire looking at historic claims with fresh eyes. It's rarely the original preparer who raises it, which is exactly why a second, independent look matters.

The general principle

What voluntary correction generally involves

UK tax law provides routes to amend a return or otherwise put HMRC on notice of an error, and doing so before HMRC opens its own enquiry is consistently treated more favourably than the same correction happening under compliance action. The exact route, timeline and any penalty position depend on how the original claim was wrong, how it was filed, and current HMRC practice. That's a job for a specialist adviser working from your actual position, not a general page.

Why a former adviser's involvement complicates this

Getting a second opinion matters more here than almost anywhere else

If the claim in question was prepared by an adviser who's still acting for you, or by one you've since moved on from, it's worth getting an independent read from someone with no stake in defending the original work. This is one of the situations where the choice of who reviews it matters as much as the review itself. See our adviser register for firms checked against Companies House and published terms, rather than simply returning to whoever built the claim in the first place.

Decision helper

Your situationUsually fitsNot this

General unease, no specific error identified yet→An independent review of the claim as filed→Waiting to see if HMRC ever raises it

Review confirms a genuine error→Specialist advice on correcting it before HMRC does→Filing the next claim and hoping it isn't noticed

HMRC has already opened an enquiry on it→This is now enquiry territory, not voluntary disclosure→Treating it as still proactive

Alternatives and limitations

If HMRC has already opened formal enquiry correspondence on the claim in question, the proactive window has generally closed and this is a different situation: see what happens once an HMRC enquiry has opened. And if this concern surfaced because a buyer or investor is looking at your claims history, see R&D claims under due diligence for how that process tends to run.

Talk it through

Need another perspective?

Describe where things stand in a sentence or two, and we'll tell you whether it's something we can help with. There's no charge for this.

What happens next

A person on our team reads it. A sentence or two is enough to start.
If we can help, we introduce you to a specialist partner we have vetted and tell you who they are.
No charge and no obligation at any point. You decide whether to go further.

Adam Parker

Founder of Muswell Rose Consulting Ltd, which trades as Established Finance · former Managing Director of Penny, an invoice finance business, with 15+ years across mortgages, commercial finance and fintech lending.

Last updated: 15 September 2026

Practical questions

Before you get in touch

Is it better to correct a wrong R&D claim myself or wait to see if HMRC finds it?

Correcting it yourself. Across UK tax, an error you put right before HMRC finds it is generally treated more favourably.

Who should review a past R&D claim I am worried about?

Someone who wasn't involved in preparing the original claim, especially if that adviser still acts for you.

Can I still voluntarily correct a claim once HMRC has opened an enquiry on it?

Not in the same way. Once an enquiry is open, it's generally enquiry territory rather than voluntary disclosure.

What information do I need?

To start, just a description of what’s actually happening in the business. If it progresses, the specialist partner will ask for the usual things: recent accounts, a sense of turnover and trading history, and details of the specific need.