United Kingdom vs Ireland: R&D relief compared

Companies operating in both the United Kingdom and Ireland, and their advisors, compare these two schemes often. Both pay a credit to companies with no tax to set it against, and both ask companies that have not claimed recently to notify in advance, but the rates, cash timing, cost rules, claim windows and review process all differ. This page sets them side by side and computes one set of costs under both.

At a glance

Point	United Kingdom	Ireland
Scheme and administering body	Merged R&D expenditure credit (RDEC) scheme and enhanced R&D intensive support (ERIS), for accounting periods beginning on or after 1 April 2024. HM Revenue and Customs (HMRC)	R&D corporation tax credit. Office of the Revenue Commissioners (Revenue)
Form of benefit	Taxable expenditure credit. ERIS gives an additional deduction and a payable credit	Corporation tax credit, payable in instalments
Headline rates	Merged scheme: 20% expenditure credit on qualifying expenditure, taxable. ERIS: an extra 86% deduction (a total deduction of 186%) and a payable credit worth up to 14.5% of the surrenderable loss	30% of qualifying expenditure for accounting periods beginning on or after 1 January 2024. 35% where the corporation tax return filing date is on or after 23 September 2027, which typically means accounting periods ending on or after 31 December 2026
Refundability	Yes. Payable credits are capped at £20,000 plus 300% of the company's relevant PAYE and National Insurance liabilities	Yes. Paid in three instalments. The first is the greater of 50% of the claim or a fixed threshold: €75,000 for periods commencing on or after 1 January 2025 that end before 31 December 2026; €87,500 where the 35% rate applies
Who can claim	Companies within the charge to UK Corporation Tax that carry out qualifying R&D. The merged scheme is open to companies of any size. ERIS is for loss-making SMEs whose relevant R&D expenditure is at least 30% of total relevant expenditure	Companies within the charge to Irish corporation tax that carry on qualifying R&D activities
Definition of qualifying work	A project qualifies if it seeks an advance in science or technology by resolving scientific or technological uncertainty. HMRC applies the government's guidelines on the meaning of R&D for tax purposes	Systematic, investigative or experimental activities in a field of science or technology that are basic research, applied research or experimental development, seek to achieve scientific or technological advancement, and involve the resolution of scientific or technological uncertainty
Registration or approval step	Claim notification if 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. An additional information form with every claim	First-time claimants, and companies that have not claimed in the previous 3 years, notify Revenue on a prescribed form at least 90 days before the claim
Claim deadline	Within 2 years of the end of the accounting period the claim relates to, in the Company Tax Return	Within 12 months of the end of the accounting period in which the expenditure was incurred, on the corporation tax return
Written description required	The additional information form describes the projects and breaks down qualifying costs: for each project, the main field of science or technology, the baseline, the advance sought, the uncertainties and how the project sought to overcome them	The claim is made in the research and development panel of the Form CT1. Any required pre-filing notification describes the R&D activities. Keep records made at the time of the uncertainty, the work to resolve it and the expenditure
Review body and time limit	HMRC compliance check, opened as an enquiry into the Company Tax Return, for most companies within 12 months of delivery. Discovery assessments within 4 years of the end of the accounting period, 6 years if careless, 20 years if deliberate	Revenue compliance intervention under the Code of Practice for Revenue Compliance Interventions. Revenue may make or amend an assessment within 4 years after the end of the chargeable period in which the return is delivered, with no time limit where the return was not full and true

Where the schemes differ in practice

How the credit turns into cash

The merged scheme credit is taxable; it is set against the Corporation Tax liability of the period, limited by the PAYE cap, and the balance is paid (merged scheme). Under section 766C the Irish credit is paid in three instalments irrespective of the company's corporation tax liability, each, at the company's election, offset against tax or repaid. The limits by reference to corporation tax paid and payroll liabilities that applied under section 766B do not apply (payable credit instalments).

Two advance notifications on different clocks

A UK company need not notify if it claimed for an accounting period ending within the three years before the last date of that period; without a required notification the company is not entitled to claim (claim notification). An Irish claim made without a required pre-filing notification is not valid. With the 12 month claim deadline, the notice has in practice to be given within about nine months of the period end (how to claim in Ireland, Irish deadlines).

Which costs qualify, and where the work may be done

In the UK 65% of payments to unconnected staff providers and subcontractors qualify, as do consumable items, data licences and cloud computing services. Relief for contracted out R&D and externally provided workers is generally limited to work carried out in the UK, and the merged scheme has no restriction for grant-funded expenditure (UK qualifying expenditure, subcontracting and overseas costs). Irish payments to unconnected persons qualify up to the greater of 15% of the company's own qualifying expenditure and €100,000, and to universities up to the greater of 5% and €100,000. Expenditure met by grant assistance and general overheads are excluded, and the activities must be carried on within the State or another EEA state (Irish qualifying expenditure).

How long the claim window stays open

A UK claim may be made, amended or withdrawn within 2 years of the end of the accounting period. If the additional information form is not submitted before the Company Tax Return, HMRC will remove the R&D claim from it, and late claims are accepted only where the delay was caused by circumstances beyond the company's control (UK deadlines). In Ireland the second and third instalments are claimed in the returns for the following two accounting periods, each within 12 months of the end of that period (Irish deadlines).

How each tax authority reviews a claim

HMRC selects claims for compliance checks on a risk basis and runs a mandatory random enquiry programme. A UK appeal must be made within 30 days (HMRC compliance checks). Revenue selects claims for compliance interventions on a risk basis and may consult any person with expertise in the field, having first informed the company. An overclaimed credit is recovered as corporation tax with interest, and an appeal goes to the Tax Appeals Commission within 30 days of the notice of assessment (Revenue audits).

Illustrative example

Illustrative example. Aldersey Instruments, a hypothetical company, has a 12 month accounting period ending 31 December 2025 and spends 400,000 on one qualifying project: 350,000 in staff costs of employees wholly engaged in the work and 50,000 in consumable materials used up in testing. The figures are used in both currencies, and all of the expenditure is assumed to qualify under both schemes.

Step	United Kingdom	Ireland
Assumptions	Merged scheme, because Aldersey is not a loss-making R&D intensive SME; Corporation Tax at the main rate; relevant PAYE and National Insurance liabilities large enough that the payable credit cap does not bite	The period begins on or after 1 January 2024 and the return is filed before 23 September 2027, so the 30% rate applies; no corporation tax liability; repayment elected for each instalment
Arithmetic	20% of £400,000 = £80,000 expenditure credit. Notional tax at 25% = £20,000. Net benefit £60,000, which is 15% of qualifying expenditure	30% of €400,000 = €120,000 credit
Cash	£60,000, set against the Corporation Tax liability of the period and the balance paid, subject to the PAYE cap	First instalment: the greater of €75,000 and 50% of €120,000 (€60,000), so €75,000. Second: three fifths of the remaining €45,000, so €27,000. Third: the balance, €18,000
If the facts changed	Loss-making at the small profits rate: notional tax at 19% = £15,200, net benefit £64,800 (16.2%). A loss-making SME with R&D intensity of at least 30% could claim ERIS instead: 26.97% of £400,000 = £107,880	A return filing date on or after 23 September 2027: 35%, a credit of €140,000 and a first instalment of the greater of €87,500 and €70,000, so €87,500

Which to study first

If the company already claims in one country, read the other country's deadlines page first: cross-border teams lose claims on the calendar, not the definitions, and the two notification rules measure the three-year look-back differently. The definitions sit close together, so study the scheme where the claim is larger and then read the other's exclusions. For the money, start with the merged scheme page and the Irish instalments page, which decides when the cash arrives.

Educational material, not advice. Eligibility and treatment depend on the scheme and the facts.

United Kingdom vs Ireland