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Advisor and Practitioner Program: United Kingdom track

What a practitioner preparing UK R&D tax relief claims must master: the guidelines on the meaning of R&D and the competent professional test, the merged scheme and ERIS, the claim notification and the additional information form that names the agent, the 2-year claim deadline, and HMRC compliance checks.

Advisor and Practitioner ProgramLast reviewed 2 October 2026
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Advisor and Practitioner Program

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This track is for accountants and advisors who prepare or review R&D tax relief claims for United Kingdom clients. For accounting periods beginning on or after 1 April 2024, most companies claim under the merged R&D expenditure credit scheme, and loss-making SMEs that are R&D intensive can claim enhanced R&D intensive support (ERIS) instead. Both are administered by HM Revenue and Customs. Two gates precede the Company Tax Return: a claim notification where required, and an additional information form with every claim. That form requires the details of any agent who advised on the claim and the senior officer of the company responsible for it.

How the United Kingdom rules change the program

ModuleWhat is different in the United KingdomCountry page
Legislation and guidanceThe government's guidelines on the meaning of R&D for tax purposes, which HMRC applies; Finance Act 1998 Schedule 18; the HMRC CIRD manual; GOV.UK guidance on the merged scheme and ERIS.United Kingdom guide
Eligibility analysisA project qualifies if it seeks an advance in science or technology by resolving scientific or technological uncertainty. An advance means an advance in overall knowledge or capability in a field, not a company's own state of knowledge alone.Eligibility
Advanced calculationsMerged scheme: 20% expenditure credit, taxable, net 15% at the main rate and 16.2% for loss-making companies. ERIS: an extra 86% deduction and a payable credit worth up to 14.5% of the surrenderable loss, capped by reference to PAYE and National Insurance.Merged scheme
Technical interviewsThe interview is with the competent professional. Claims should be able to show which competent professionals judged the uncertainty and what relevant expertise they had.Documentation
Reports and narrativesFor each project described, the additional information form requires the main field of science or technology, the baseline level, the advance sought, the scientific or technological uncertainties, and how the project sought to overcome them.Additional information form
Disputes and auditsAn HMRC enquiry, called a compliance check. Information requests usually set a 30 day deadline, which can be extended on request. Appeal within 30 days, statutory review, alternative dispute resolution or the First-tier Tribunal.HMRC compliance checks
Ethics, integrity and fee arrangementsThe agent is named on the claim notification and the additional information form. A company cannot show reasonable care merely by appointing an agent. Whether contingent fees are permitted depends on the professional body the advisor belongs to; see knowyourfees.org.Briefing and evaluating an advisor

Forms and deadlines

Form or stepDeadline or ruleCountry page
Claim notificationIf claiming for the first time or the last claim was more than 3 years ago: within 6 months of the end of the period of account. Where required and not made, the company is not entitled to make an R&D claim for the accounting period.Claim notification
Additional information formWith every claim, before the Company Tax Return. If not submitted before the return, HMRC will remove the R&D claim from the return.Additional information form
The claim: CT600 with supplementary page CT600LMade, amended or withdrawn within 2 years of the end of the accounting period it relates to. Late claims only in limited circumstances, where the delay was caused by circumstances beyond the company's control.How to claim
Company Tax Return and paymentReturn due 12 months after the end of the accounting period; Corporation Tax due 9 months and one day after it for companies not paying by instalments.Deadlines
Enquiry windowFor most companies, within 12 months of the date the return was delivered; for members of large groups, within 12 months of the filing date.Reviews and audits

Key rules to know

The three-year exemption is counted from the end of the window. A company is not required to notify if it has made an R&D claim in an accounting period ending within the three years before the last date of the notification period, disregarding claims made in amended returns submitted on or after 1 April 2023 for periods beginning before that date.

Location decides contracted out costs. For accounting periods beginning on or after 1 April 2024, relief for contracted out R&D and externally provided workers is generally limited to work carried out in the UK. Overseas work qualifies only where conditions necessary for the R&D are not present in the UK and it would be wholly unreasonable to replicate them; cost and availability of workers are not qualifying reasons. See subcontracting and overseas costs.

Who contracted whom, and who was subsidised. R&D is contracted out where a company engages another person to undertake activities, and it is reasonable to assume that the company intended or contemplated that R&D of that sort would be done to meet its requirements. The merged scheme contains no restriction for subsidised or grant-funded expenditure; earlier periods follow the legacy SME and RDEC rules.

ERIS is a group measure and a choice. The intensity ratio is measured across the company and its connected companies, and an R&D intensive SME may elect to claim under the merged scheme rather than ERIS.

Worked example

Illustrative example. Thornfield Analytics Ltd, a hypothetical loss-making SME with a year to 31 March 2026, has never claimed, so the practitioner submits the claim notification by 30 September 2026. Qualifying expenditure is £400,000: staffing costs of £300,000, £100,000 paid to an unconnected UK subcontractor entering at 65% as £65,000, and consumables of £35,000. Total relevant expenditure is £1,000,000, so the intensity ratio is 40%. The trading loss before relief is £600,000 and relevant PAYE and National Insurance liabilities are £90,000.

StepERISMerged scheme (the alternative election)
ReliefAdditional deduction 86% of £400,000 = £344,000; enhanced expenditure £744,000Expenditure credit 20% of £400,000 = £80,000, taxable
Loss positionTrading loss after the deduction £944,000; surrenderable loss is the lower of £944,000 and £744,000 = £744,000Notional tax deducted at the small profits rate (19%) for a loss-making company
CashPayable credit 14.5% of £744,000 = £107,880 (26.97% of qualifying expenditure)Net 16.2% of £400,000 = £64,800
Cap£20,000 plus 300% of £90,000 = £290,000, not binding under either route

ERIS is worth £43,080 more, so the practitioner claims ERIS, and £200,000 of unsurrendered loss is carried forward. Before the CT600 and CT600L are filed, the additional information form describes both projects, enters the costs by category, and names the finance director as the senior officer responsible and the practitioner as agent.

Self-check questions

Answer each question, then open it to compare.

A new client with a period of account to 31 December 2026 has never claimed. By when must the claim notification be submitted, and what happens if it is missed?
Within 6 months of the end of the period of account, so by 30 June 2027. Where a claim notification is required and is not made within the claim notification period, the company is not entitled to make an R&D claim for the accounting period.
The Company Tax Return containing the claim was filed before the additional information form. What does HMRC do?
If the additional information form is not submitted before the Company Tax Return, HMRC will remove the R&D claim from the return. The form can then be submitted and the claim made again by amending the return, within 2 years of the end of the accounting period.
A client has eight projects. How many must be described on the additional information form?
Enough projects to account for at least 50 percent of the qualifying expenditure, with a minimum of 3 and a maximum of 10, including any project that accounts for more than 50 percent of the expenditure. With 1 to 3 projects, all of them are described.
A loss-making SME has relevant R&D expenditure of £300,000 and total relevant expenditure of £1,200,000. Can it claim ERIS?
Not on this year alone. ERIS is for loss-making SMEs whose relevant R&D expenditure is at least 30 percent of total relevant expenditure, and £300,000 is 25 percent of £1,200,000. A company that qualified as R&D intensive in its previous accounting period and claimed ERIS or the pre-April 2024 enhanced relief is treated as meeting the intensity condition for the following period even if it falls below 30 percent.
A client says that appointing you as agent means it has taken reasonable care. Is that right?
No. A company cannot show reasonable care merely by appointing an agent; it must take reasonable steps to check the return. Penalties for an inaccuracy are up to 30 percent of the potential lost revenue for careless, 70 percent for deliberate and 100 percent for deliberate and concealed inaccuracies, with reductions for unprompted and prompted disclosure.

Official sources

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Educational content only, not tax advice. See the disclaimer.