HMRC’s R&D Enquiry Team Just Changed: What WMBC Taking Over From ISBC Means for Your Claim

If you're about to file an R&D claim — or you're bracing for a possible HMRC R&D enquiry — it's worth knowing that the team reviewing R&D claims has changed. In March 2026, HMRC confirmed it is winding down the "volume compliance" approach run by its Individuals and Small Business Compliance (ISBC) unit and moving R&D enquiry work back into its Wealthy and Mid-sized Business Compliance (WMBC) directorate. It's a quiet administrative change with real consequences for how new claims get reviewed.

Here's what has changed, why it matters, and how to be ready.

What actually changed

Since 2022, most R&D enquiries were handled by ISBC under a "volume compliance" model — high numbers of standardised checks, largely run through templated letters. HMRC has now announced it is ending that approach. Over roughly the following six months, ISBC officers are being redeployed, and R&D compliance is being consolidated within WMBC.

In practice this reinstates the pre-2022 position, when WMBC handled R&D enquiries and the focus was on more complex or higher-risk cases rather than sheer volume. HMRC's own practice note for how officers should review claims — CIRD80525 — now applies to officers in both ISBC and WMBC.

Why HMRC made the switch

The volume approach was a response to a well-documented problem. HMRC told the House of Commons Public Accounts Committee that it had moved to checking around one in five R&D claims — up from a historic enquiry rate of roughly 1% — after estimating that error and fraud accounted for a significant share of the relief paid out. You can read HMRC's rationale in its published approach to Research and Development tax reliefs.

The volume model was effective at raising the enquiry rate, but widely criticised — including by the tax profession — for catching legitimate claims in templated challenges and for being difficult to engage with. Moving the work to WMBC signals a shift back towards more targeted scrutiny of genuinely complex risks.

What a WMBC enquiry looks like in practice

For claimants, the change of team usually means a change of tone. WMBC has historically run enquiries on a more individual basis:

• A named caseworker owns the case, rather than correspondence bouncing between an anonymous team.
• More willingness to engage directly — including conference calls to talk through the technical work, instead of relying purely on letters.
• A focus on the substance of the R&D — the technological uncertainty and the advance sought — rather than a checklist run at scale.

That is generally good news if your claim is well-evidenced and you can explain the technology. It can be tougher if the underlying claim is thin, because a named officer engaging in detail is harder to satisfy with boilerplate answers.

What this means for your claim

The fundamentals of surviving an HMRC compliance check haven't changed — but the move to WMBC raises the premium on being able to defend the substance of your claim in a conversation, not just on paper.

• Keep contemporaneous records. Our guide to the R&D compliance records to keep sets out exactly what to retain, from technical notes to timesheets.
• Make your technical narrative specific. Name the scientific or technological uncertainty, the advance sought, and why it wasn't readily deducible by a competent professional.
• Get your Additional Information Form right. Figures in your HMRC R&D Additional Information Form must reconcile to your tax return — mismatches remain a common enquiry trigger.
• Know the process. If you want the full picture of how checks unfold, see our comprehensive guide to HMRC enquiries and compliance checks.

Going forward, R&D enquiry work is being resourced through WMBC — so a claim you file now is more likely to be reviewed by a named caseworker taking a more engaged, technically-focused approach. Either way, the discipline is the same: answer the standing questions on their merits, not with boilerplate. For what may change next, see our preview of the Autumn Budget 2026 and R&D tax relief.

Frequently Asked Questions

Is ISBC still handling R&D enquiries?

HMRC announced in March 2026 that it is winding down ISBC's volume-compliance approach to R&D and consolidating R&D compliance within its WMBC directorate over roughly the following six months, with ISBC officers being redeployed. The change is about how HMRC resources new enquiry work rather than a promise about any individual open case.

What is WMBC?

WMBC is HMRC's Wealthy and Mid-sized Business Compliance directorate. It handled R&D enquiries before 2022 and tends to run cases with a named caseworker and direct engagement, focusing on more complex risks rather than high-volume templated checks.

Does this change reduce my chance of an R&D enquiry?

Not necessarily. HMRC has been checking around one in five R&D claims. The change is about who runs the enquiry and how, not a signal that scrutiny is easing — a well-evidenced claim remains the best protection.

What should I do if I receive an enquiry letter?

Don't reply off the cuff. Gather your contemporaneous evidence, reconcile your figures, and consider specialist R&D tax relief enquiry support before you respond — early framing of the technical case matters more under a named caseworker.