The terms
"RDEC", "merged scheme" and "ERIS" are adviser shorthand
A director or FD owed R&D relief is usually asking something practical: can I still claim if I got a grant, does my contractor's work count, what changed in 2024? The scheme names are shorthand that formed around the legislation, not around those questions. The rules changed substantially in April 2024, but a lot of what's published either assumes you already know the terms or was written before the reform and never updated. This page explains them in plain terms.
What actually changed
One merged scheme replaced the old SME/RDEC split
Before the reform, which scheme you claimed under depended on your company's size and whether your R&D was subsidised or contracted out, splitting claims across a separate SME scheme and RDEC. For accounting periods beginning on or after 1 April 2024, that split is largely gone. Most companies, regardless of size, claim through the merged scheme: a single R&D Expenditure Credit (RDEC), an above-the-line credit calculated as a percentage of qualifying R&D spend (see gov.uk's "The Merged Scheme: R&D Expenditure Credit (RDEC)").
The exception
ERIS sits alongside the merged scheme, with a predecessor that ran a year earlier
Enhanced R&D Intensive Support (ERIS), under that name and its current legislative footing, applies for accounting periods beginning on or after 1 April 2024, the same start date as the merged scheme (HMRC manual CIRD121000). Periods beginning on or after 1 April 2023 but before that sit in an older transition window: HMRC's manual describes a separate, retrospective provision letting R&D-intensive SMEs claim a higher tax credit rate under the old SME scheme, with its own mechanics distinct from ERIS. Confirm that directly with an adviser rather than assuming ERIS's rules apply retroactively. From 1 April 2024, ERIS itself uses a 30% R&D-intensity threshold, down from a stricter 40% under the predecessor arrangement (CIRD123000). There's also a one-year grace period if a company qualified and claimed under the intensity condition last period but slips just under the threshold this period, so a single quiet year doesn't knock a genuinely R&D-heavy business out of the more generous rate.
Worth being precise about: the intensity ratio isn't just "R&D spend divided by turnover." It's qualifying R&D expenditure, including that of any connected companies, divided by total relevant expenditure for the period, also including connected companies. Two businesses with the same-looking R&D budget can land either side of the threshold depending on group structure. Confirm the exact figure with an adviser rather than estimating from headline numbers.
Working out which applies to you
Three questions decide it, and the checker answers them for you
The routing itself is mostly mechanical: it turns on your accounting period start date, whether you're loss-making, and roughly how R&D-intensive you are. The scheme checker walks through those three questions and gives you a straight answer, including a real calculation of your intensity ratio if you have rough figures to hand.
In practice
Three things the scheme mechanics change
What this page doesn't cover
Notification and the Additional Information Form are separate
Both are procedural steps that sit on top of whichever scheme applies. This page covers the scheme mechanics underneath those filings. For the filings themselves, see:
- the notification three-year rule
- what happens if you miss the notification window
- the Additional Information Form
- the notification deadline checker
Alternatives and limitations
Qualifying work is a separate question
None of this changes whether your work qualifies as R&D in the first place. That's a technical-uncertainty question covered on R&D claim services. And scheme mechanics are genuinely fact-specific in places, particularly the overseas and contracted-out rules, so treat this page as the map, not the final word for a borderline case.
