UK R&D tax relief now runs through two schemes. For accounting periods beginning on or after 1 April 2024, most companies claim the merged R&D expenditure credit: a 20% credit worth 15p per £1 of qualifying spend at the 25% corporation tax rate, 16.2p for loss-makers and companies paying tax at 19%, and as low as 14.7p where marginal relief applies. Loss-making SMEs whose relevant R&D expenditure is at least 30% of their total relevant expenditure can claim Enhanced R&D Intensive Support (ERIS) instead, worth up to 26.97p per £1 in cash.
The relief comes with a compliance regime to match. First-time claimants, and companies returning after a gap in claims, must notify HMRC or make the claim itself by the notification deadline, every claim needs an Additional Information Form, and HMRC checked around one in six claims in 2023-24, its latest published figure. This page collects our guides to all of it, each written and reviewed by a chartered adviser.
Start with your situation
New to R&D tax relief. Begin with what counts as qualifying R&D, then which costs qualify, then which scheme applies to your company. Read the claim notification requirement early: for a first claim, the deadline can pass before anyone mentions R&D relief to you.
Already claiming. The rules changed substantially for accounting periods beginning on or after 1 April 2024. Check your position against the merged scheme, and if you hold grant funding, read grant funding and R&D tax relief: the old restrictions are gone, and much of the advice still published online is out of date.
Worried about an enquiry. Start with HMRC R&D enquiries: what to expect, how the process runs and how to respond. Enquiry support is included in every LimestoneGrey engagement as standard; if the claim under enquiry was prepared by someone else, HMRC enquiry defence is the standalone engagement that covers it. If you already suspect a past claim was wrong, voluntary disclosure sets out what coming forward first is worth.
Loss-making and R&D-intensive. You may be entitled to the most generous rate in the system. Read the ERIS guide and test yourself against the 30% threshold with the ERIS intensity calculator.
In financial difficulty. The going concern condition decides whether a merged-scheme credit arrives as cash and whether an ERIS claim can be made at all, and the order of events matters: R&D tax relief when a company is in trouble sets out what to do before an administrator or liquidator is appointed, and what can still be claimed afterwards.
An accountant with a client that may qualify. We act as the specialist R&D arm of accountancy practices, on referral or under the practice’s own name — R&D tax support for accountants sets out how each route works and what happens to the client relationship.
The rules, sector by sector
The legislation is the same whatever you build, but the arguments that decide a claim are not. Where the boundary falls in software development is a different question from proving an advance in life sciences or biotech, and different again for the contract analysis that runs through aerospace and defence or the trial records behind a manufacturing claim. Our sector guides set out the complication we meet most often in each.
Quick answers and tools
The questions we answer in full, each on a page of its own, are indexed at R&D tax relief questions. Shorter questions are answered in the FAQ. Terms defined in one line each, with a link to the guide behind every one, are in the R&D tax relief glossary. The paragraphs of HMRC’s own manual these guides rely on, each with HMRC’s title for it and the date it was last revised, are collected in our CIRD reference index. HMRC’s annual statistics, ranked by sub-region with Welsh and sector cuts, are on our R&D relief by sub-region page. For working estimates on your own numbers, use the R&D tax credit calculator, the ERIS intensity calculator or the claim notification deadline checker — all free, and collected on our tools page.
If you would rather talk than read, talk it through with a chartered adviser. We will tell you which scheme applies, what a claim would involve and whether it is worth making, and the fee is agreed before any work starts.
Position depends on when the accounting period begins, tax position and R&D intensity. The 30% ratio includes connected companies.
Written by Matthew Jones ACA CTA. Last reviewed October 2026.
