The UK R&D tax credit scheme was merged into a single regime from April 2024. The old "SME scheme" (with 14% surrender rate for tax-loss-making companies) was rolled into the new merged scheme with a 20% headline RDEC rate. Profit-making companies get a 20% above-the-line credit on qualifying R&D expenditure (effective net rate ~15% after corporation tax). Loss-making companies can surrender the credit for a cash refund, but at materially lower rates than the old SME scheme — real cash benefit of ~10% for most software-development companies. The "R&D-intensive SME" rule (40%+ of total expenditure on R&D) preserves higher rates for genuine technology companies. Eligibility hinges on whether the work meets HMRC's definition of qualifying R&D — technological uncertainty resolved through systematic investigation.
The post-April-2024 merged scheme
For accounting periods starting on or after 1 April 2024:
- Single rate: 20% taxable above-the-line credit on qualifying R&D expenditure.
- Effective benefit for profit-making: 20% × (1 - 25% corp tax) = 15% net.
- For loss-making companies: can surrender for cash refund. Rate depends on R&D intensity.
- R&D-intensive SMEs (40%+ of expenditure on R&D): separate higher-rate scheme. 27% effective rate.
Eligibility — what HMRC defines as R&D
For UK R&D tax credit purposes, qualifying R&D must:
- Seek an advance in science or technology. Not just commercial application of known technology.
- Resolve scientific or technological uncertainty. Something experts in the field don't know how to do.
- Be carried out by competent professionals. Demonstrated expertise in the relevant field.
- Use a systematic investigation methodology. Documented, iterative approach.
For software companies specifically (where most disputes arise):
- Building a website using existing frameworks: usually NOT R&D.
- Optimising existing algorithms with creative new approaches: COULD be R&D.
- Building novel ML/AI systems with technical uncertainty: USUALLY R&D.
- Integrating multiple systems in standard ways: usually NOT R&D.
- Developing genuinely new algorithms (search, recommendation, etc.) where industry doesn't know the answer: USUALLY R&D.
Qualifying expenditure
Allowable R&D costs include:
- Staff salaries for staff directly engaged in R&D (apportioned by time).
- Subcontractor costs (typically at 65% of expenditure under the new scheme).
- EPW (Externally Provided Workers): agency contractors, etc.
- Consumables: materials, fuel, light, water used in R&D.
- Software licences used directly for R&D.
- Pension and NI on R&D staff.
NOT allowable:
- Capital expenditure (separate Capital Allowance regime).
- Rent and property costs.
- Patents, marketing, and commercialisation costs.
- Customer-facing development of standard solutions.
Worked example — UK software startup
£500k turnover SaaS company, £250k R&D expenditure, £20k profit
| Total expenditure | £480,000 |
| R&D expenditure | £250,000 |
| R&D as % of total: £250k / £480k = 52% | >40% threshold |
| Qualifies as R&D-intensive SME | Yes |
| RDEC-style credit: £250,000 × 27% (intensive rate) | £67,500 |
| Net cash flow improvement (above-the-line, P&L credit) | ~£50,000 after CT |
For this R&D-intensive SME, the credit is roughly 10% of total turnover or 25% of payroll — material.
Same SaaS company, but £100k R&D out of £500k total (non-intensive)
| R&D as % of total: £100k / £500k = 20% | Below 40% threshold |
| Standard merged-scheme RDEC: £100,000 × 20% | £20,000 above-the-line credit |
| Effective net (after 25% corp tax) | ~£15,000 |
Still meaningful, but the R&D-intensive status meaningfully increases the value for genuinely innovative companies.
The claims process
- Determine eligibility. Apply HMRC's 4-part R&D test to specific projects.
- Calculate qualifying expenditure. Apportion staff time, identify allowable costs.
- Prepare the claim narrative. Document the technological uncertainty, the systematic methodology, and the personnel competence. This is the critical document for HMRC review.
- Submit on Corporation Tax return. Include the claim in the CT600 + supporting schedules.
- HMRC processes: typically 4-6 weeks for processing, longer if HMRC opens an enquiry.
- Cash refund (if surrendering loss) or P&L credit (if profit-making) lands in the company.
Common rejection reasons
- Project is commercial development, not technical R&D. "Building a website" isn't R&D regardless of complexity.
- Uncertainty was about business viability, not technology. "Will customers want this?" isn't R&D.
- No documentation of systematic investigation. "We just figured it out" doesn't meet the methodology test.
- Incompetent personnel claim. Junior developers learning a framework isn't R&D by competent professionals.
- R&D was outsourced and the company isn't the developer. If you're paying for off-the-shelf work, you can't claim — though qualifying subcontracted R&D is allowable at 65%.
Engaging an R&D specialist adviser
R&D claims are complex enough that most small companies engage a specialist adviser. Two cost models:
- Contingency: 20-30% of the credit value. No upfront cost. Adviser bears the risk of an unsuccessful claim.
- Fixed fee: £2,000-£10,000 depending on complexity. Lower total cost if the claim is straightforward.
HMRC has cracked down significantly on rogue R&D claims (2022-2025) and now scrutinises more claims. Reputable advisers, good documentation, and conservative claim positions are essential.
Sources and methodology
R&D scheme reforms from Finance Act 2024 (Sections 9-22). Eligibility criteria from HMRC's Corporate Intangibles Research and Development Manual (CIRD). For specific R&D claim advice, an R&D-specialist accountant is required — see the tax adviser editorial recommendation. The methodology page documents sources.
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