The Compliance Risk That Is Not on Your 2026 Radar
Ask a UK practice owner what has consumed 2026 and you will hear about quarterly updates, Companies House identity verification, the move of AML supervision towards the FCA and a Budget landing on the 28th of October. What you will rarely hear mentioned is research and development tax relief.
That silence is the problem. R&D relief has changed character over the last three years. It used to be a technical conversation about whether a project advanced science or technology. It is now, first and foremost, an administrative regime with hard gates. Miss a gate and the relief is gone, regardless of how good the underlying science was, how strong the records are, or how sympathetic the inspector might be.
For firms that carry even a handful of innovative limited company clients, that shift turns R&D into a practice risk rather than a tax opportunity. And unlike most tax risks, this one is usually created inside the practice, by a diary entry that was never made.
The Six-Month Gate That Ends Claims Before They Start
For accounting periods beginning on or after the 1st of April 2023, most companies must tell HMRC in advance that they intend to claim, using a claim notification. The window opens on the first day of the period of account and closes six months after the end of that period of account. Miss it and the claim is invalid. There is no reasonable excuse route, no late notification process and no appeal that rescues the position.
Work through what that means for a normal client list:
- A March 31st 2026 year end must be notified by the 30th of September 2026. That is this week.
- A June 30th 2026 year end must be notified by the 31st of December 2026, in the middle of Self Assessment season.
- A December 31st 2026 year end must be notified by the 30th of June 2027.
Note where those dates fall. They sit inside your busiest quarter, and they arrive long before the corporation tax return that would normally prompt anyone to think about R&D. The Corporation Tax filing deadline is twelve months after the period end. The notification deadline is six. Firms that pick up R&D when the CT600 is prepared are structurally too late.
There is an exemption for some companies that have claimed recently, but it is narrower than most people assume. It depends on claims made in a defined three calendar year lookback, and claims made by amending a return are not always counted. Treating the exemption as a general safety net for existing claimants is how good claims get lost. If there is any doubt, notify.
The Additional Information Form Is Not Optional Either
The second gate is the Additional Information Form. It must reach HMRC before or on the same day as the Company Tax Return that contains the claim. If it does not, HMRC will remove the claim from the return. Practices have seen claims stripped out simply because the form went in the day after filing.
The form also requires named individuals: the senior officer of the company who takes responsibility for the claim, the competent professional who can speak to the technical uncertainty, and details of any agent who advised on it. That last point deserves attention if you work alongside a specialist R&D boutique. HMRC now has a clear view of who touched the claim, and your client will have a clear view of who they blame if it fails. Make sure your engagement letters say explicitly who owns notification, who owns the technical narrative, who owns the form and who owns the filing.
HMRC's Advance Assurance Pilot: A Window That Closes in 2027
There is an upside to all this scrutiny. On the 18th of May 2026, HMRC launched a targeted advance assurance pilot. It lets eligible SMEs ask HMRC for its view on up to two specific high risk or complex areas of a claim before the claim is filed. It is voluntary, free of charge, and it runs for twelve months from launch.
The four areas it covers are:
- whether a project meets the definition of R&D for tax purposes
- whether overseas expenditure qualifies for relief
- whether relief can be claimed where the work is contracted out between companies
- whether the company qualifies for exemption from the PAYE and National Insurance contributions cap
Each application covers one project and one area, so two questions means two applications. HMRC aims to respond within 40 calendar days where the information provided is complete. The company must be an SME, must be carrying out or planning R&D in the period concerned, and must not yet have claimed for that period. Companies are shut out if they have an open Corporation Tax enquiry, have used a disclosable tax avoidance scheme, are categorised as a corporate serious defaulter, or have applied for full claim advance assurance for the same period.
Two cautions are worth passing to clients. First, if assurance is refused, there is no right of appeal and no second application. You can still claim in the return, but you will be doing so knowing HMRC's view. Second, assurance is not a claim. Notification and the Additional Information Form still apply exactly as before, and the 40 day turnaround means this is not a tool to reach for a fortnight before a deadline.
Used selectively, on the genuinely judgmental cases where a client is nervous and the money is material, it is a good deal. Used as a default step on every straightforward claim, it will simply burn capacity you do not have in January.
What to Do in the Next Two Weeks
- Run a list, not a memory test. Query your client base for limited companies with any history of R&D claims, development spend, technical staff, grant funding or capitalised development costs. Memory does not scale past about twenty clients.
- Diarise notification deadlines, not filing deadlines. Add a task at period end plus five months for every candidate company, so the deadline surfaces with a month of slack rather than on the day.
- Deal with the 31st of March 2026 year ends now. Their notification window closes on the 30th of September 2026.
- Notify where you are unsure. Notification costs a small amount of time. Missing it costs the entire claim.
- Sequence the paperwork. Make it a standing rule that the Additional Information Form is submitted before the CT600, never after, and that the reference is saved to the client record.
- Identify the competent professional early. If nobody at the client can explain the technical uncertainty in their own words, you have an evidence problem rather than a form problem.
- Shortlist advance assurance candidates. Look for overseas costs, contracted out arrangements, PAYE and NIC cap issues and first time claimants with real uncertainty. The pilot window closes in 2027.
- Review your engagement letters and your PII position wherever a third party R&D adviser is involved in claims you file.
The Practice Management Point
None of this is difficult tax. It is deadline hygiene applied to a relief where the penalty for poor hygiene is total. The firms that get caught out are not the ones with weak technical knowledge, they are the ones relying on a spreadsheet and a good memory across a client list that has grown faster than their processes.
If your practice management system already tracks accounts, Corporation Tax and confirmation statement deadlines, R&D claim notification belongs in exactly the same place, with the same automatic reminders and the same visibility across the team. Recording it centrally means it survives a staff change, a busy January and a client who only mentions their new product line in passing.
The profession has spent 2026 absorbing change it did not choose. R&D notification is one of the few risks on the list that you can eliminate entirely this month, with nothing more than a query, a diary entry and a short email to a handful of clients.
