R&D Disclosure Service: HMRC Clarifies Independent Treatment of SME and RDEC Claims

HMRC has updated guidance confirming that correcting an invalid SME R&D claim and making a replacement RDEC claim are dealt with independently, offering businesses a second chance to recover relief after amendment deadlines have expired.

R&D Disclosure Service: HMRC Clarifies Independent Treatment of SME and RDEC Claims

HMRC has updated its guidance on the R&D disclosure service where a company has incorrectly claimed relief under the SME scheme and the time limit for amending its corporation tax return has expired, confirming that correcting an invalid SME claim and making a replacement RDEC claim are now dealt with independently. The clarification offers relief to businesses facing historic R&D relief errors, but comes with important operational considerations for accountants advising affected clients.

What Has Changed

Where an SME R&D claim is found to be invalid, the company should disclose the error through the R&D disclosure service.

If it wishes to claim Research and Development Expenditure Credit (RDEC) for the same accounting period, a separate claim process applies through submissions to HMRC's designated mailbox. This dual-path approach had previously caused uncertainty among practitioners about sequencing, timing and evidence requirements.

The new guidance removes a significant ambiguity. Previously, businesses and their advisers were unsure whether correcting an SME claim automatically precluded a subsequent RDEC claim for the same period, or whether the two processes could run in parallel.

HMRC has now confirmed that the two matters will be dealt with independently, opening a route for companies to recover relief that would otherwise be permanently lost.

Why This Matters

The R&D tax relief regime comprises two schemes: the SME scheme (offering up to 130% relief on qualifying expenditure) and the RDEC scheme (offering 20% relief, available to larger companies and SMEs in certain circumstances).

Companies that identify historic errors in SME R&D claims should act promptly, as HMRC has confirmed that correcting an invalid SME claim and making a replacement RDEC claim are separate processes, so businesses should carefully consider the timing and evidence required before approaching HMRC.

The practical significance is substantial. Many SMEs claimed R&D relief during the pandemic and post-pandemic periods without comprehensive documentary support. Some claims have now been queried by HMRC or flagged by accountants on review. If the original claim cannot be amended (because the statutory amendment window has closed), companies faced an effective loss of relief. HMRC's new guidance provides a legitimate second chance—albeit under a stricter regime (RDEC) and with reduced relief (20% rather than 130%).

What Accountants Must Do

Practitioners with clients holding potentially invalid SME R&D claims should:

Review the file: Identify any SME claims made in previous years and assess whether they would withstand scrutiny under HMRC's current guidance on qualifying activities, documentation and the statutory definition of research and development.

Consider timing carefully:

Businesses should carefully consider the timing and evidence required before approaching HMRC. The disclosure service requires a formal notification, and evidence of qualifying expenditure must be robust. A botched disclosure or weak RDEC submission could result in no relief at all.

Gather contemporaneous evidence: Both SME and RDEC claims demand detailed technical and contemporaneous evidence of the qualifying R&D activities, project costs, staff effort, and the nature of the advance sought. For historic years, this evidence may be sparse. Building a credible narrative and assembling what documentation exists is essential.

Engage HMRC early (if appropriate): For borderline cases, consider seeking HMRC guidance before submitting a formal disclosure. Some practitioners have reported that proactive dialogue with HMRC has improved outcomes, particularly where the company is acting in good faith.

The Broader Context

The First-tier Tribunal recently considered a care home operator in Tanglewood Care Services Ltd v HMRC [2026] UKFTT 1137, deciding that operational or commercial challenges do not automatically qualify for R&D relief.

The tribunal's decision is a reminder that responding to a complex commercial or operational challenge does not automatically qualify for R&D relief. This case illustrates HMRC's hardening stance on R&D claims and reinforces why disclosure of errors, backed by clear evidence of genuine scientific or technological advance, is preferable to defending an indefensible position.