Your R&D Tax Adviser Must Now Be Registered With HMRC — What to Check Before You Claim

There's a new question worth asking before you let anyone file an R&D claim on your behalf: is your adviser registered with HMRC? Since 18 May 2026, R&D tax adviser registration has been mandatory — any adviser paid to deal with HMRC for you must be on HMRC's register. For a scheme that has attracted more than its share of rogue agents, it's a useful new filter for choosing who handles your claim.

Here's what the rule is, and what it means for you as the company making the claim.

What's changed

HMRC has introduced mandatory registration for tax advisers. Any adviser or agent who is paid to interact with HMRC on behalf of clients now has to register — including firms that already hold an agent services account, and advisers based overseas who act for UK taxpayers.

Registration began on 18 May 2026 and is being rolled out in stages through to 31 March 2027. In broad terms:

• Advisers without an existing HMRC agent or online account fell into the first wave from 18 May 2026.
• Existing agents with a Self Assessment or Corporation Tax account (but no agent services account) can register from 18 August 2026.
• Later windows run through to the end of the rollout in March 2027.

Registration itself is free, and each adviser has three months from their window opening to get an agent services account. HMRC's own guidance on who must register and when sets out the detail.

Why this matters for R&D claims especially

R&D tax relief has been HMRC's problem child for compliance. After estimating significant levels of error and fraud in the scheme, HMRC moved to checking around one in five claims and, in 2026, shifted R&D enquiry work to its WMBC directorate for more targeted scrutiny. A recurring theme in the worst cases was unregulated, sometimes fly-by-night "R&D specialists" filing weak or inflated claims and leaving the company to face the enquiry.

Mandatory registration is part of HMRC's answer. It doesn't make every registered adviser good — but it removes the ability to operate entirely off HMRC's radar, and it sits alongside the requirement to name the agent who prepared your claim on the Additional Information Form. Your adviser is now visible to HMRC, by name, on every claim.

What happens if an adviser isn't registered

The consequences fall on the adviser, but they affect you. An adviser who needs to register and doesn't cannot interact with HMRC on your behalf. If they keep trying after being told to stop, HMRC can apply sanctions — financial penalties and temporary or permanent bans from acting as an agent.

In practice: if the person filing your R&D claim isn't registered, at best your claim stalls, and at worst you're relying on someone HMRC may bar mid-process. That's a poor position to be in when a claim is already under more scrutiny than ever.

What to check before you appoint an R&D adviser

Registration is now one of several basic checks worth making when choosing an R&D adviser:

1. Are they HMRC-registered to act as a tax agent (or clearly within a later registration window)?
2. Will they be named on your AIF — and are they comfortable being so?
3. Do they hold professional body membership (CIOT, ICAEW, ACCA) and professional indemnity cover?
4. Do they stand behind the claim — will they handle any HMRC enquiry, not disappear once the fee is paid?
5. Is the fee reasonable and transparent, rather than a large contingent slice with no enquiry support?

Zest is a registered, qualified adviser — R&D tax relief is our specialism, not a bolt-on — and we're named on the claims we prepare. If you're reviewing who files your next claim, registration is a sensible place to start.

Frequently Asked Questions

Does my R&D adviser have to be registered with HMRC?

Yes. Since 18 May 2026, any adviser paid to interact with HMRC on your behalf must register with HMRC, with the rollout completing by 31 March 2027. That includes advisers who prepare and file R&D tax relief claims.

What happens if I use an adviser who isn't registered?

An unregistered adviser who is required to register cannot interact with HMRC for you, and faces sanctions if they try. Your claim could stall, or you could be left mid-enquiry if HMRC bars them. Check registration before you appoint anyone.

How can I tell if an adviser is legitimate?

Beyond HMRC registration, look for professional body membership (CIOT, ICAEW, ACCA), professional indemnity insurance, willingness to be named on your Additional Information Form, and a commitment to support you through any HMRC enquiry rather than walking away after filing.