If your business invests time and money into developing new products, processes, or software, you are almost certainly eligible for R&D tax credits. The UK government designed this relief to reward technical innovation. Yet most eligible businesses never claim. Why? Because the rules are complex, the documentation is demanding, and HMRC has become significantly more aggressive in its compliance checks.
This guide is for UK business owners, directors, contractors, and partners who want to understand R&D tax credits from first principles. It covers the merged scheme rules for accounting periods starting on or after 1 April 2024, the Enhanced R&D Intensive Scheme (ERIS), what qualifies as R&D, how to calculate your claim, and why working with an r&d tax credit specialist is the difference between a successful claim and a costly HMRC enquiry.
As ICAEW qualified accountants, we have submitted hundreds of R&D claims for UK businesses of every shape, from a two-person software startup in Shoreditch to a precision engineering firm in the Jewellery Quarter in Birmingham. This guide reflects what we have learned. It is comprehensive, practical, and up to date for 2025/26.
What Are R&D Tax Credits?
R&D tax credits are a corporation tax relief. They reward companies that invest in research and development. The relief reduces your corporation tax bill. If your company is loss-making, it can receive a cash payment from HMRC instead.
The scheme is not just for scientists in white coats. It covers software development, engineering improvements, manufacturing process innovation, agricultural technology, and much more. If your project sought to resolve scientific or technological uncertainty, it qualifies.
The Two Pre-Merger Schemes (Historical Context)
Before 1 April 2024, there were two separate schemes. The SME scheme offered a 186% enhanced deduction (230% before April 2023) plus a payable tax credit. The large company RDEC scheme offered a 15% above-the-line credit. This split caused confusion and meant companies near the SME thresholds had to navigate complex rules.
The Merged Scheme from 1 April 2024
For accounting periods starting on or after 1 April 2024, the two schemes merged into a single, simplified RDEC-like scheme for all companies. The headline rate is 20% of qualifying R&D expenditure, taken as a taxable credit against corporation tax. For loss-making companies, the payable credit rate is 15% (reduced from the pre-merger SME payable credit rate of 14.5% for the merged scheme, though the calculation mechanics differ).
The key change: the enhanced SME deduction (186%) is gone. All companies now use the RDEC mechanism. But there is a critical exception for loss-making R&D-intensive companies, we cover that in the ERIS section below.
Does Your Business Qualify for R&D Tax Credits?
This is the question we answer most often. The answer depends on your project, not your sector. HMRC defines R&D using guidelines from the Department for Business, Energy and Industrial Strategy (BEIS). The definition has not changed with the merger.
The HMRC Definition of R&D
A project qualifies as R&D if it seeks to achieve an advance in science or technology. The advance must be in the field of science or technology relevant to your business. It does not need to be a world-first. It can be an advance in your own field or industry.
HMRC also requires that the project involved scientific or technological uncertainty. That means the solution was not readily deducible by a competent professional working in the field. If you had to experiment, test, prototype, fail, and iterate, you likely faced uncertainty.
What Does NOT Qualify
Routine development does not qualify. Neither does work that merely uses an existing product or process in a standard way. For example:
- Customising a standard software package for a client
- Routine testing of existing products
- Market research or consumer surveys
- Arts, humanities, or social science projects (including economics)
- Production of commercial prototypes without technical uncertainty
Common Qualifying Projects by Sector
We have prepared successful claims for businesses in these areas:
- Software and technology: Developing new algorithms, cloud infrastructure, AI models, cybersecurity tools, or data processing systems. A startup in the Northern Quarter in Manchester building a real-time payment reconciliation engine, that qualified.
- Manufacturing and engineering: Designing new production processes, improving material efficiency, developing new alloys or composites, automating complex assembly. A precision engineering firm in Leeds Dock reducing waste in CNC machining, that qualified.
- Life sciences and healthcare: Developing medical devices, diagnostic tools, drug delivery systems, or laboratory equipment. A biotech firm in Edinburgh's Old Town working on a novel blood glucose sensor, that qualified.
- Agriculture and food technology: Developing new crop treatments, automated harvesting systems, alternative proteins, or food preservation methods. A vertical farming company in Bristol's Harbourside, that qualified.
- Construction and materials: Developing new building materials, structural systems, or energy efficiency solutions. A construction materials firm in Glasgow's Merchant City developing a low-carbon concrete mix, that qualified.
If you are unsure whether your project qualifies, speak to an R&D tax credit specialist before you start the claim process. A quick review of your project notes can save months of wasted effort.
The Merged R&D Scheme: How It Works
For accounting periods starting on or after 1 April 2024, the merged scheme applies to all companies. Here is how the calculation works.
The RDEC Credit Rate
The RDEC credit is 20% of your qualifying R&D expenditure. This credit is treated as taxable income. So the net benefit is less than 20% after corporation tax.
For a profitable company paying 25% corporation tax, the net benefit is approximately 15%. For a company paying 19% (small profits rate), the net benefit is approximately 16.2%.
Worked Example: Profitable Company
Let us use a realistic example. Nexus Engineering Ltd is based in the Digbeth area of Birmingham. It develops advanced automation systems for food packaging. In the year ended 31 March 2025, Nexus spent £63,400 on qualifying R&D costs.
| Item | Amount |
|---|---|
| Qualifying R&D expenditure | £63,400 |
| RDEC credit (20%) | £12,680 |
| Tax on RDEC credit (25% corporation tax) | £3,170 |
| Net corporation tax reduction | £9,510 |
Nexus Engineering reduces its corporation tax bill by £9,510. If it had paid £50,000 in corporation tax before the claim, it now pays £40,490. The company also gets a credit in its corporation tax return (CT600) that reduces the tax payable.
Worked Example: Loss-Making Company (Non-Intensive)
BrightCode Software Ltd is a startup in the Baltic Triangle in Liverpool. It has developed a new type of predictive analytics tool for logistics companies. In its first year, it spent £92,800 on qualifying R&D but made no sales. It is loss-making.
| Item | Amount |
|---|---|
| Qualifying R&D expenditure | £92,800 |
| RDEC credit (20%) | £18,560 |
| Payable credit rate (15% of RDEC credit) | £13,920 |
| Less: tax on RDEC credit (deemed income) | £3,712 |
| Net cash payment from HMRC | £10,208 |
BrightCode receives a cash payment of £10,208 from HMRC. This is a direct injection into the business, no tax bill to offset. That cash can fund the next phase of development.
Note: the payable credit for loss-making companies under the merged scheme is 15% of the RDEC credit, not 20%. The calculation above reflects the rules for accounting periods starting on or after 1 April 2024.
The Enhanced R&D Intensive Scheme (ERIS)
There is a critical exception to the merged scheme. Loss-making companies that are R&D-intensive can claim under a more generous regime. This is the Enhanced R&D Intensive Scheme (ERIS).
What Is R&D-Intensive?
A company is R&D-intensive if its qualifying R&D expenditure is at least 30% of its total operating expenditure. This threshold applies for the accounting period. If you meet this test and are loss-making, you can claim a higher payable credit rate.
ERIS Payable Credit Rate
Under ERIS, the payable credit rate is 14.5% of the qualifying R&D expenditure (not the RDEC credit). This is significantly more generous than the standard merged scheme payable credit.
Worked Example: ERIS Claim
NanoCoat Materials Ltd is based in the Kelvin area of Glasgow. It develops advanced surface coatings for medical implants. In the year ended 31 March 2025, it spent £147,200 on qualifying R&D. Total operating expenditure was £420,000. R&D intensity is 35% (above the 30% threshold). The company is loss-making.
| Item | Amount |
|---|---|
| Qualifying R&D expenditure | £147,200 |
| ERIS payable credit (14.5% of qualifying spend) | £21,344 |
| Net cash payment from HMRC | £21,344 |
Under the standard merged scheme, NanoCoat would have received approximately £16,192. The ERIS claim delivers £21,344, an additional £5,152. That is a meaningful difference for a growing company.
ERIS claims require additional disclosure in the CT600 and supporting evidence of R&D intensity. An R&D tax credit specialist can help you determine whether your company qualifies and prepare the necessary documentation.
Qualifying R&D Costs: What You Can Claim
The merged scheme has tightened the definition of qualifying costs. You can only claim for costs that are directly attributable to qualifying R&D projects. Indirect or overhead costs are no longer allowable.
Allowable Costs Under the Merged Scheme
- Staff costs: Salaries, wages, employer's NI, and employer pension contributions for employees directly engaged in R&D. You must apportion time if staff split their work between R&D and non-R&D activities.
- Consumables: Materials, utilities, and other items consumed or transformed in the R&D process. This includes software licenses used directly for R&D, prototype materials, and testing supplies.
- Externally provided workers: Costs of subcontractors or agency workers engaged in R&D. Under the merged scheme, you can only claim 65% of these costs (reduced from the pre-merger SME scheme rules). This is a significant change.
- Contributions to independent R&D: Payments to universities, charities, or other organisations for R&D activities. Again, only 65% of these costs are allowable.
- Software license costs: Cloud computing costs and software licenses used directly for R&D are now explicitly allowable.
Costs That Are No Longer Allowable
- Subcontracted R&D: Under the pre-merger SME scheme, you could claim 100% of subcontractor costs. Under the merged scheme, only 65% is allowable. This is a major reduction for businesses that rely heavily on external developers or engineers.
- Overheads and indirect costs: Rent, utilities (unless consumed in R&D), administrative support, and general overheads are no longer qualifying costs.
- Capital expenditure: You cannot claim R&D tax credits on capital equipment. But you may be able to claim capital allowances (AIA or Full Expensing) on the same assets. We cover this in the corporation tax guide.
Staff Cost Apportionment: A Practical Example
GreenField AgriTech Ltd is based in the Stokes Croft area of Bristol. It employs four engineers who split their time between R&D and commercial project work. Total staff costs for the four engineers are £180,000. Based on timesheets and project records, 62% of their time was spent on R&D.
Qualifying staff costs: £180,000 × 62% = £111,600.
HMRC expects to see timesheets, project logs, or other contemporaneous records to support this apportionment. A retrospective estimate will not withstand an enquiry. This is where a specialist adds real value, ensuring your records are robust from the start.
The Importance of Technical Narrative and Supporting Evidence
HMRC now requires a detailed technical narrative for every R&D claim. This is not optional. The narrative must explain the scientific or technological advance you sought, the uncertainties you faced, and the work you undertook to overcome them.
What a Good Technical Narrative Contains
- A description of the baseline: what was the state of the art before your project?
- The advance sought: what were you trying to achieve that was not already known?
- The uncertainties: what technical challenges did you face that were not readily deducible?
- The work undertaken: what experiments, prototypes, tests, or iterations did you perform?
- The outcomes: what did you learn, and did you achieve the advance?
The narrative should be written in plain English. Avoid jargon. A non-specialist at HMRC should be able to understand the technical challenge. We have seen claims rejected because the narrative was too vague or too technical.
Supporting Evidence HMRC Expects
- Project plans and design documents
- Technical specifications and requirements
- Test results and analysis
- Timesheets and resource allocation records
- Emails or meeting notes discussing technical challenges
- Prototype photographs or videos
- Software version control logs
HMRC can and does open enquiries into R&D claims. In 2023/24, HMRC opened over 10,000 compliance checks on R&D claims. A well-prepared claim with a strong technical narrative and supporting evidence is your best defence. An R&D tax credit specialist will help you build this evidence base before you submit the claim.
Common Pitfalls and HMRC Enquiry Risks
R&D tax credits are a high-risk area for HMRC. The relief is generous, and the rules are complex. HMRC has invested heavily in compliance. Here are the most common mistakes we see.
Claiming for Non-Qualifying Activities
Routine development, standard customisation, and commercial prototyping without technical uncertainty do not qualify. We have seen claims rejected because the company described "developing a new website" or "improving an existing product" without demonstrating technical uncertainty. Be precise about what made your project technically challenging.
Incorrect Cost Allocation
Including overheads, rent, or administrative costs that are no longer allowable under the merged scheme. Or claiming 100% of subcontractor costs when only 65% is allowable. These errors trigger enquiries.
Poor Record Keeping
HMRC expects contemporaneous records. If you submit a claim based on retrospective estimates, you are inviting an enquiry. We recommend setting up project tracking from day one of any R&D project.
Overlooking the Associated Companies Rule
For the purposes of the small profits rate and R&D intensity calculation, you must include the employees and turnover of associated companies. If you own or control other companies, you cannot ignore them. This is a common trap for groups of companies.
Not Using a Specialist
This is the biggest mistake. R&D tax credits are not a DIY exercise. The rules change frequently. The technical narrative requires specialist input. The financial calculations are nuanced. A specialist ensures your claim is accurate, defensible, and optimised. The cost of a specialist is almost always outweighed by the value of a successful claim and the avoided cost of an HMRC enquiry.
How to Choose an R&D Tax Credit Specialist
Not all accountants are R&D specialists. General practice accountants may not have the technical knowledge to prepare a robust claim. Here is what to look for.
ICAEW Qualification and R&D Experience
Look for a firm that is ICAEW qualified and has a track record of R&D claims. Ask how many claims they have submitted in the last 12 months. Ask about their enquiry rate. A good specialist will have a low enquiry rate because their claims are well-prepared.
Sector Knowledge
Your specialist should understand your industry. A software R&D claim is very different from a manufacturing claim. The technical narrative must reflect the specific challenges of your field. We have prepared claims for software firms in Shoreditch, engineering firms in Sheffield's Kelham Island, and biotech firms in Cambridge. Sector knowledge matters.
Fixed Fees and Transparency
R&D claims are often charged as a percentage of the benefit. This is standard. But the percentage should be transparent and agreed upfront. Avoid firms that charge a high percentage or add hidden fees. A typical fee is 15% to 25% of the benefit, depending on complexity.
End-to-End Service
Your specialist should handle everything: the technical narrative, the financial calculation, the CT600 submission, and any HMRC enquiries. Some firms prepare the claim but leave the submission to your accountant. This creates gaps and increases enquiry risk. We recommend a firm that handles the entire process.
Our services page explains how we work with UK businesses on R&D claims. We offer a free initial review to assess whether your project qualifies.
R&D Tax Credits and Other Reliefs
R&D tax credits interact with other reliefs. You need to understand these interactions to avoid missing out or double-claiming.
Capital Allowances
You cannot claim R&D tax credits on capital equipment. But you can claim capital allowances on the same assets. Full Expensing allows a 100% deduction on main-rate plant and machinery. The Annual Investment Allowance (AIA) is £1,000,000 per year. You should claim both where applicable, R&D credits on revenue costs, capital allowances on capital costs.
Patent Box
If your R&D leads to a patented invention, the Patent Box regime allows you to pay a reduced 10% corporation tax on profits from that patent. R&D tax credits and Patent Box can be claimed together. But the calculations interact. You need a specialist to optimise both.
Employment Allowance
If you claim R&D tax credits on staff costs, you still claim the Employment Allowance on your employer NI. The two reliefs are independent. But the Employment Allowance is limited to £10,500 per year and is only available if your employer NI bill was below £100,000 in the previous tax year.
Share Schemes and SEIS/EIS
If your company is raising investment through SEIS or EIS, the R&D tax credit claim does not affect the investor relief. But the timing of the claim can affect your company's cash flow and valuation. We cover this in our incorporation and structure blog.
Action Checklist: How to Prepare an R&D Tax Credit Claim
Follow this checklist to prepare a robust R&D tax credit claim. Tick off each item before you submit.
- Identify qualifying projects. Review your project list for the accounting period. Identify any project that sought to resolve scientific or technological uncertainty. Document the advance sought and the uncertainties faced.
- Calculate qualifying costs. Gather staff costs, consumables, subcontractor costs (65% allowable), software licenses, and externally provided workers. Exclude overheads, capital expenditure, and non-qualifying activities.
- Prepare the technical narrative. Write a clear, plain-English description of each qualifying project. Include the baseline, the advance sought, the uncertainties, the work undertaken, and the outcomes. Support with evidence.
- Calculate the RDEC credit. Multiply qualifying costs by 20%. Adjust for the taxable nature of the credit. If loss-making, calculate the payable credit (15% of RDEC credit, or 14.5% of qualifying costs if ERIS applies).
- Check R&D intensity. If loss-making, calculate R&D expenditure as a percentage of total operating expenditure. If 30% or above, you may qualify for ERIS. This requires additional disclosure.
- Complete the CT600. Enter the RDEC credit in the relevant box. Include the additional information form (AIF) if required. The AIF is mandatory for all claims from 1 August 2023.
- Submit the claim. Submit the CT600 and supporting documents to HMRC. Keep copies of everything. HMRC can open an enquiry up to 12 months after submission.
- Monitor for enquiries. If HMRC opens an enquiry, respond promptly with the supporting evidence. A well-prepared claim should survive an enquiry. But the process can take months. A specialist can manage this for you.
If this checklist feels overwhelming, you are not alone. Most business owners do not have the time or expertise to prepare an R&D claim. That is why we exist. Contact us for a free initial review of your R&D projects. We will tell you whether you qualify and what the claim could be worth.