How to Claim Ireland’s 35% R&D Tax Credit: SME Eligibility & Revenue Audit-Readiness Guide

Most SME owners hear “R&D tax credit” and picture a lab coat. That’s the wrong picture. If your team spent last year fixing a manufacturing process that kept producing inconsistent results or building software functionality nobody was sure would actually work, that’s R&D in Revenue’s eyes — and it might be worth real money back.

Here’s the part that should get SME attention: Revenue’s own figures show small and medium companies file the majority of R&D claims, yet large companies still take home the bulk of the money. That gap isn’t about eligibility. It’s about SMEs either not claiming or claiming without the documentation to defend it.

The rate just went up. For accounting periods beginning on or after 1 January 2026, the credit is 35% of qualifying expenditure, up from 30%. This guide covers who qualifies, exactly how to file, and — the part most R&D content skips — what happens if Revenue opens an enquiry into your claim.

The SME Claims Gap: What the Numbers Actually Show

This is worth pausing on before you decide whether the credit applies to a business your size. Revenue’s most recent claims data show small and medium companies filed 1,444 R&D claims against just 187 from large companies – SMEs made almost 90% of all claims by volume. But those SME claims accounted for only €888m in expenditure, against €3.8bn from large companies.

That’s not a sign SMEs don’t qualify. It’s a sign SMEs are claiming smaller amounts less consistently or leaving eligible work out of the claim altogether — often because the documentation feels like more effort than it’s worth or because nobody in the business realised a process fix or a software build counted as R&D in the first place.

The practical takeaway: if your business is already doing technically uncertain work as part of normal operations, the gap isn’t in eligibility; it’s in capture. A claim built properly from the start, at the new 35% rate, closes that gap without needing to be a large multinational.

What Changed in Budget 2026: The Rate Increase Explained

Budget 2026, announced in October 2025, increased the R&D tax credit rate from 30% to 35% for accounting periods beginning on or after 1 January 2026. It’s the second increase in two years — the rate moved from 25% to 30% for periods starting from 1 January 2024 and now to 35%.

The first-year payment threshold went up alongside it, from €75,000 to €87,500. That threshold matters more than it sounds: it’s the minimum amount a company can receive as a cash refund in year one of a three-year instalment claim, regardless of the total credit size.

• 25% → 30% → 35%: the rate timeline across accounting periods from pre-2024 through 2026
• First-year payment threshold: €75,000 → €87,500
• The Department of Finance has also flagged further reform — including changes to subcontracting rules and qualifying expenditure definitions — through an upcoming R&D Compass, so expect this regime to keep evolving

Do You Qualify? The SME Eligibility Test

Three baseline conditions apply before you even get to the technical test:

• Your company must be within the charge of Irish corporation tax
• The R&D activity itself must take place in Ireland, the EEA, or the UK
• You don’t need to own the resulting intellectual property, and the work doesn’t need to succeed — a failed experiment can still qualify.

Then there’s the science test, which is where most SME owners switch off because it’s usually written in adviser language. Stripped down, Revenue is asking four things about the work:

• Was it systematic, investigative, or experimental — not just “we tried a few things and picked one”, but a structured attempt to solve a problem?
• Did it sit in a field of science or technology?
• Was the goal a genuine scientific or technological advancement — not just new to your business, but pushing past what was already known or achievable?
• Was there real technological or scientific uncertainty at the outset — meaning a competent professional in the field couldn’t have predicted the outcome in advance?

That last point is the one worth sitting with. “We’d never built this before” isn’t the same as “this was technologically uncertain.” If an experienced engineer could have looked at the brief and known exactly how to solve it, Revenue wouldn’t see it as qualifying – even if it were new territory for your business, specifically.

This is also broader than lab research. Process improvements, software development, and product iteration all qualify, provided the outcome was genuinely uncertain when you started.

A useful gut check: ask whether your team hit a genuine technical obstacle they had to work through or whether they simply followed a known method to a result they could already predict. The first is R&D. The second, however much effort it took, generally isn’t, and being honest about that distinction upfront is what keeps a claim defensible later.

What Counts as Qualifying Expenditure

Once the activity qualifies, several cost categories can go into the claim:

• Staff costs — and under current rules, 100% of an employee’s pay can qualify if 95% or more of their time went on eligible R&D work
• Subcontractor costs, within statutory limits
• Materials and consumables used in the R&D activity
• Plant and machinery eligible for wear-and-tear allowances, to the extent they’re used for R&D
• Construction or refurbishment of buildings used for qualifying R&D, subject to conditions

On subcontracting specifically, there’s a cap on how much of your qualifying expenditure can come from subcontracted work, and separate rules govern transferring the benefit to a key employee rather than the company. If you’re leaning on contractors for a significant share of the project, it’s worth checking where you sit against that limit before you build the claim around it — this is exactly the kind of detail a tax adviser should sign off on.

How to Claim: The CT1 Process, Step by Step

The claim itself runs through your CT1 corporation tax return, but the groundwork starts well before you file.

Here’s what that looks like with the current rates. A company with €300,000 of qualifying R&D expenditure claims a credit of €105,000 at 35%.

The first-year threshold does the heavy lifting for smaller claims — it’s why the increase to €87,500 matters more to SMEs than it might to a large multinational running a much bigger claim.

One more timing detail worth flagging: the 90-day pre-notification isn’t just a formality. Revenue expects it to include a broad outline of the R&D activities involved and an estimate of the qualifying expenditure, so it needs the same groundwork as the claim itself, just started earlier. Treat it as the first real deadline in the process, not a box to tick after the project is already finished.

1. Confirm whether pre-notification applies. If this is your first claim or you haven’t claimed in any of the previous three accounting periods, you need to notify Revenue at least 90 days in advance. days before filing the claim. Miss this window, and you lose the claim for that period, no exceptions.
2. Carry out and document the science test assessment as the work happens — not retrospectively once the accounting period has closed.
3. File the claim within the CT1 return for the relevant accounting period.
4. Meet the 12-month deadline, which runs from the end of the accounting period in which the expenditure was incurred.
5. Elect how each instalment is treated: offset against corporation tax due, or paid out in cash.

Year	Instalment	Amount
Year 1	Greater of €87,500 or 50% of the claim (€52,500)	€87,500
Year 2	Three-fifths of the remaining €17,500 balance	€10,500
Year 3	Remainder	€7,000

Passing the Accounting Test: Documentation Revenue Actually Wants

The science test gets a project through the door. The accounting test is what determines whether the claim holds up once it’s filed — and it’s almost entirely about documentation quality, not documentation volume. Revenue wants:

• Contemporaneous project logs that show the technical challenge and how it was worked through — written at the time, not reconstructed for the claim
• Timesheets, or another defensible method, apportioning staff time to R&D activity specifically
• A documented cost-allocation methodology — a spreadsheet total with no explanation of how it was built won’t hold up
• Contracts and invoices for subcontractors, materials, and equipment
• Internal correspondence — emails, meeting notes, Slack threads — that shows the technical uncertainty as it existed in real time

Revenue Audit-Readiness: What Triggers a Review and How to Prepare

This is the part most R&D guides skip entirely, and it’s the part that actually protects your claim.

Revenue has four years from the end of the year in which the claim is made to open an audit. That’s a long window, and it means claim documentation needs to survive well past the filing date — not just exist at the point of submission.

Two things tend to trigger a closer look:

• Whether the activity genuinely meets the science test — “innovative for us” isn’t the same as “technologically uncertain”, and Revenue knows the difference
• Whether the cost apportionment between R&D and non-R&D work is actually defensible, rather than an estimate applied after the fact

The single biggest weakness Revenue enquiries exposure is retrofitted documentation — a claim file built at filing time instead of built while the work was happening. If your technical lead’s account of the project and your finance team’s cost breakdown don’t quite line up, that mismatch is exactly what an enquiry will find and query.

The upside of doing this properly: a well-documented claim, with contemporaneous records and a clear cost-allocation method, tends to keep any revenue adjustment narrow — confined to specific disputed cost lines rather than putting the whole claim at risk.

In practice, audit-readiness is less about a specific document type and more about a habit: log the technical problem the week it comes up, not the month before the CT1 deadline. A short note in a project tracker, written while the uncertainty is still live, does more for a claim’s credibility than a polished write-up assembled afterwards ever will.

Common SME Mistakes That Cost the Credit

Most claims that run into trouble aren’t rejected outright — they’re narrowed, delayed, or quietly under-claimed because of a handful of avoidable errors.

• Waiting until the CT1 deadline to start building the claim, which leaves no time for a proper technical write-up
• Treating all technical work as qualifying R&D, instead of isolating the specific elements that were genuinely uncertain
• Missing the 90-day pre-notification window on a first-time or lapsed claim
• Having no clear method for splitting staff time between R&D and non-R&D work

FAQs

What is the R&D tax credit rate in Ireland in 2026?

35% of qualifying expenditure, for accounting periods beginning on or after 1 January 2026 — up from 30% previously. This is on top of the standard corporation tax deduction for the same costs.

Can a small business or sole trader claim the R&D tax credit?

The credit is only available to companies within the charge of Irish corporation tax, so unincorporated sole traders don’t qualify directly. A sole trader planning R&D-heavy work may want to weigh incorporation against this and other factors.

How far back can the revenue audit an R&D tax credit claim?

Revenue has four years from the end of the year in which the claim is made to carry out an audit, so claim documentation should be retained well beyond the filing date.

Do I need to own the resulting intellectual property to claim the credit?

No. Ownership of any IP resulting from the R&D activity isn’t a requirement for the claim.

What happens if revenue queries or reduces my claim?

A well-documented claim, with contemporaneous technical records and a clear cost-allocation method, typically narrows any revenue adjustment to specific disputed cost lines rather than putting the entire claim at risk.

Can I claim the R&D tax credit alongside a grant (Enterprise Ireland, IDA, Horizon Europe)?

Yes, subject to conditions. Revenue has indicated it won’t require a company to separately evidence the science test where the project already holds one of these grants and meets the relevant SME size and claim-value thresholds.

Is there a minimum company size to claim?

No minimum size applies — the credit is available to SMEs and large companies alike. However, the scheme’s design (pre-notification, science and accounting tests) tends to favour claimants who plan their documentation from the start.

The Bottom Line

None of this replaces a tax adviser’s sign-off on the science test — that’s a specialist call, and it should stay one. But the groundwork underneath every R&D claim is bookkeeping cost records, and a clean CT1 filing, and that’s exactly where we come in. If your records are audit-ready year-round, the R&D claim on top of them is a much easier conversation.