This track is for finance managers, tax leads and accountants preparing an Irish R&D corporation tax credit claim in-house. The credit is administered by the Office of the Revenue Commissioners (Revenue) and gives a credit against corporation tax for qualifying R&D expenditure; credit that cannot be used can be paid out in three instalments. Three things change the program's shape: a 12 month claim window that a pre-filing notification can shorten, a wholly and exclusively cost test, and a benefit that arrives over three years whatever the tax position.
How the Ireland rules change the program
| Module | What is different in Ireland | Country page |
|---|---|---|
| Scheme mechanics | A corporation tax credit of 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. | Ireland overview |
| Cost capture | Expenditure incurred wholly and exclusively in carrying on R&D activities. Plant and machinery qualifying for wear and tear allowances qualifies to the extent it is used for R&D. | Eligible expenditure |
| Staff time apportionment | Staff costs are apportioned according to the proportion of time spent on qualifying R&D activities, supported by records such as timesheets; general management, administration and non-R&D supervision are not qualifying expenditure. | Eligible expenditure |
| Contractors and overseas costs | Unconnected subcontractors up to the greater of 15 percent of the company's own qualifying expenditure and €100,000; universities and institutes up to the greater of 5 percent and €100,000. The activities must be carried on within the State or another EEA state. | Eligible expenditure |
| Grants and subsidised expenditure | Expenditure met directly or indirectly by grant assistance or any other assistance from the State, an EU institution or any other state is not qualifying expenditure. | Revenue guidelines |
| Calculations | Rate times qualifying expenditure, then the instalment split: the first instalment is the greater of €75,000 (€87,500 where the 35 percent rate applies) and 50 percent of the credit, the second is three fifths of the remainder, the third is the balance. | Payable credit instalments |
| Working with technical teams | The science test: activities in a prescribed field, systematic, investigative or experimental, seeking scientific or technological advancement and resolving uncertainty a competent professional could not readily resolve. | Science test |
| Filing and deadlines | Pre-filing notification at least 90 days before the claim where the company has not claimed in any of the 3 preceding accounting periods; the claim is made on the Form CT1 within 12 months of the end of the accounting period. | Deadlines |
| Reviews and audits | Revenue selects claims for compliance interventions on a risk basis under its Code of Practice, with Level 1 compliance support interventions, Level 2 risk reviews and audits, and Level 3 investigations. | Revenue audits |
Forms and deadlines
| Form or step | Timing | Country page |
|---|---|---|
| Pre-filing notification, prescribed form through Revenue Online Service | At least 90 days before the claim, where no claim was made in any of the 3 accounting periods immediately preceding the period of the claim. | How to claim |
| Form CT1, research and development panel | The return is due by the 23rd day of the ninth month after the end of the accounting period where filed electronically. The R&D credit claim must be made within 12 months of the end of the accounting period. | Deadlines |
| Instalment elections | On the CT1 for each instalment: offset against corporation tax or repayment. The second and third instalments are claimed in the returns for the following accounting periods. | Payable credit instalments |
| Revenue amendment window and records | Revenue may make or amend an assessment within 4 years after the end of the chargeable period in which the return is delivered. Records are kept for 6 years. | Revenue audits |
Key rules to know
The notification clock is the first deadline. Companies claiming for the first time, or that have not claimed in the previous 3 years, must notify Revenue in advance, at least 90 days before the claim, using a prescribed form. A claim made without the required pre-filing notification is not a valid claim.
Wholly and exclusively is the cost test. General overheads such as rent, rates, insurance and administration are excluded, while costs directly consumed in the R&D such as power and laboratory supplies may be apportioned.
Subcontracting is capped twice and must be notified. A company that subcontracts R&D to an unconnected person must notify that person in writing that it is claiming the credit, and the subcontractor may not then claim.
Worked example
Illustrative example. Shannon Instruments Limited, a hypothetical company with an accounting period ending 31 December 2025, has not claimed before. Its finance team files the pre-filing notification by 23 June 2026, at least 90 days before the Form CT1 it plans to file by 23 September 2026.
| Cost | Amount | Treatment | Qualifying |
|---|---|---|---|
| Engineers' emoluments, 70% of time on qualifying R&D per timesheets | €500,000 | Staff costs, apportioned | €350,000 |
| Test equipment, 100% R&D use | €60,000 | Plant and machinery qualifying for wear and tear allowances | €60,000 |
| Materials, laboratory power and project-only cloud | €50,000 | Wholly and exclusively | €50,000 |
| Unconnected Irish contractor, notified in writing | €150,000 | Capped at the greater of 15 percent of own qualifying expenditure (€69,000) and €100,000 | €100,000 |
| University research agreement in the State | €30,000 | Within the greater of 5 percent (€23,000) and €100,000 | €30,000 |
| Rent, insurance and administration | €80,000 | General overheads, excluded | 0 |
| Enterprise Ireland grant towards the engineers' costs | (€90,000) | Met by grant assistance, not qualifying | (€90,000) |
| Qualifying expenditure | €500,000 |
Own qualifying expenditure before subcontracting is €460,000, which is why the contractor cap is €100,000 rather than 15 percent. The period began on 1 January 2025 and the return is filed before 23 September 2027, so the rate is 30%: the credit is €150,000. Shannon has no corporation tax liability and elects repayment. The first instalment is the greater of €75,000 and 50 percent of the credit, so €75,000, on the 2025 Form CT1. The remaining €75,000 splits into a second instalment of three fifths, €45,000, on the return for 2026, and a third of €30,000 on the return for 2027.
Had the period ended on 31 December 2026, the return filing date would be 23 September 2027 and the 35% rate would apply: a credit of €175,000 with a first instalment of €87,500, then €52,500 and €35,000. The contractor's €50,000 excess and the rent earn no credit in either case.
Related country guide pages
Self-check questions
Answer each question, then open it to compare.
Your company last claimed the R&D tax credit five accounting periods ago and wants to claim for the period ending 31 December 2025. What must it do first, and by when in practice?
Qualifying expenditure is €500,000 for an accounting period beginning on 1 January 2025. What is the credit and how is it paid?
A company with own qualifying expenditure of €460,000 pays an unconnected Irish contractor €150,000 to carry on R&D on its behalf. How much of the contractor payment qualifies?
How does an Enterprise Ireland grant towards engineers' salaries affect the qualifying expenditure?
Which overheads can be included in Irish qualifying expenditure, and which cannot?
What records does Revenue expect for the science test and the accounting test?
Official sources
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Educational content only, not tax advice. See the disclaimer.