UK SaaS R&D tax credit 2026: the merged scheme, ERIS for loss-making indie SaaS, and how a solo founder can claim £20k-£50k back from HMRC

Most UK SaaS indie founders don't claim R&D tax credits. They assume R&D is what big companies with research labs do. They assume the qualifying activities require a PhD and a team. They assume the application process is too expensive and too risky to be worth bothering with.

All three assumptions are wrong. Under the merged R&D scheme that applies to accounting periods beginning on or after 1 April 2024, the qualifying threshold is "advance in science or technology through resolution of scientific or technological uncertainty" — which a solo SaaS founder building a non-trivial product hits regularly. Loss-making R&D-intensive SMEs (where qualifying R&D spend is at least 30% of total expenditure) get 27% of qualifying spend back as a payable cash credit under the Enhanced R&D Intensive Support (ERIS) scheme.

For a solo SaaS founder spending £80k-£120k of their year on a technically novel product, the cash claim is typically £20k-£50k. This is a tax credit, not a loan. HMRC pays it directly to your company within 8-12 weeks of approved claim.

This is the founder-side walkthrough. What qualifies, how the merged scheme works, when ERIS applies for an indie SaaS, what costs to track, and how to file without spending £5k on a "specialist consultant".

What qualifies as R&D for a UK SaaS

The HMRC test is two-step: there must be an advance in science or technology, achieved through the resolution of scientific or technological uncertainty.

For a SaaS indie founder, qualifying activities typically include:

Activity	Why it qualifies
Building a novel ML/AI integration where existing tools don't solve the problem	Resolution of technological uncertainty — competent professional couldn't have known the integration would work without trial
Custom data pipeline / ETL where standard tools fail at scale	Resolution of uncertainty around scaling, throughput, edge cases
Real-time collaboration features (CRDT, OT, custom sync)	Genuine technological uncertainty about consistency under network partition
New algorithm or data structure for a specific problem domain	Advance in computer science
Performance optimisation pushing existing tech beyond known limits	Resolution of technical uncertainty about achievability
Cross-platform compatibility solving novel issues	Resolution of platform-specific uncertainty
Security feature where existing solutions are inadequate	Advance in cryptography/security
Custom rendering/visualisation pushing browser/GPU limits	Technological uncertainty in approach

Activities that don't qualify:

• Standard CRUD app built with off-the-shelf tools (Next.js + Postgres + Stripe).
• UI design, even if it's distinctive.
• Integration of existing APIs in standard ways.
• Marketing, sales, content writing.
• Project management, ops, finance.
• Business model innovation (the what you're building) without technical uncertainty in the how.

The bar isn't "is this a hard problem to solve?" — many hard business problems don't qualify. The bar is "would a competent professional in this field need to do trial-and-error to solve this technical sub-problem?"

For a solo SaaS founder, the qualifying activities are usually:

1. The novel-integration sub-problems. Stitching together AI APIs in ways that don't yet exist as a standard pattern. Building a pipeline that handles edge cases the off-the-shelf tools don't.
2. The performance/scale sub-problems. Making something work that off-the-shelf doesn't.
3. The algorithmic sub-problems. Custom sorting, matching, scoring algorithms specific to your domain.

A typical solo SaaS year might have 2-4 distinct qualifying R&D projects, each running for 1-3 months of dev time.

ERIS — the 27% cash credit explained

For accounting periods beginning on or after 1 April 2024, Enhanced R&D Intensive Support (ERIS) applies to loss-making SMEs where qualifying R&D expenditure is at least 30% of total expenditure for the period. This is a key route for indie SaaS founders in their first 1-3 years of building.

The maths:

• You're a loss-making SME (most pre-revenue or early-revenue indie SaaS are).
• Your qualifying R&D expenditure is at least 30% of your total company expenditure.
• You can claim a payable cash credit at 14.5% of the surrendered loss.
• The surrendered loss is calculated by adding 86% of the qualifying R&D expenditure to your trading loss and surrendering the lesser of (a) the resulting loss or (b) 186% of the qualifying R&D expenditure.

Translated to founder terms:

For every £100 of qualifying R&D spend, you get ~£27 back as cash from HMRC.

If your qualifying R&D for the year is £80,000, the cash claim is approximately £21,600.

If your qualifying R&D is £150,000, the cash claim is approximately £40,500.

When ERIS applies for an indie SaaS

Stage	R&D as % of total	Loss-making?	ERIS applies?
Pre-revenue, building solo, infrastructure-heavy	80%+	Yes	Yes
First paying customers, infrastructure costs dominant	50-70%	Often yes	Yes
Steady revenue, infrastructure stable	20-30%	Sometimes	Borderline — calculate carefully
Profitable, multi-product	10-20%	No	No (use merged scheme instead)
Marketing-heavy, content-led	10-20%	Possibly	No (R&D not 30%+)

For most solo SaaS founders in years 1-2, ERIS is the right scheme. As you scale and add non-R&D spend (marketing, sales, customer success), the R&D-as-percentage-of-total drops below 30% and you switch to the merged scheme.

Qualifying costs for a UK SaaS

The HMRC eligible cost categories:

Category	What counts for SaaS	What doesn't
Staff costs	Salary + employer NIC + pension contributions for staff directly engaged in R&D	Sales, marketing, admin, finance staff; founder time spent on non-R&D activities
Subcontracted R&D	Outsourced developers / agencies doing R&D work	Standard development outsourced as a deliverable; tools/services
Externally provided workers	Agency contractors doing R&D	Standard contractors not engaged in R&D
Consumables	Software licences directly used in R&D (test environments, dev tools)	General-purpose software (Notion, Linear, GitHub if used for non-R&D)
Data licences	Datasets purchased to develop and test R&D activities	Customer/operational datasets
Cloud computing	AWS/Vercel/cloud spend on R&D environments (testing, prototyping, training)	Production hosting (post-deployment); customer-facing infrastructure
Software (cloud)	Specific R&D-stage tools	Customer-facing SaaS subscriptions
Founder's own time	Yes if paid via PAYE — proportionate to R&D activities (need timesheets)	Pure dividend-only founders cannot claim time

The founder-time question

This is the bit that catches most solo founders. You can only claim your time if you're paid through PAYE. Pure dividend-only directors cannot claim their time as an R&D cost — there's no PAYE/NIC for HMRC to calculate against.

Practical advice for solo founders: pay yourself a small salary (typically £6,240-£12,570 for tax efficiency) plus dividends. The salary pulls you into the PAYE system, which lets you claim a proportion of your time as R&D staff cost.

If you spend 60% of your year on qualifying R&D activities and you take a £12,000 salary plus £25,000 dividends, you can claim 60% of the £12,000 + employer NIC = ~£7,500 as R&D staff cost.

A worked example

Solo SaaS founder, year 1 of trading.

• Salary £12,570 + dividends £15,000 (loss-making after R&D adjustment).
• 70% of time on qualifying R&D activities (novel ML integration + custom data pipeline + real-time sync feature).
• Cloud spend: £8,000 (50% on R&D test environments, 50% on production).
• Subcontractor (3-month contract for specialist ML engineer): £18,000 (100% R&D).
• Software licences (dev tools, test environments): £2,400 (50% R&D).
• Data licences (training data): £1,500 (100% R&D).

Qualifying R&D expenditure:

Cost	Total	R&D %	Qualifying
Founder time (salary + NIC)	£13,500	70%	£9,450
Subcontractor	£18,000	100%	£18,000
Cloud (R&D portion)	£8,000	50%	£4,000
Software	£2,400	50%	£1,200
Data licences	£1,500	100%	£1,500
Total qualifying R&D			£34,150

Total company expenditure (other costs):

• Marketing: £3,000
• Customer support tools: £1,200
• Accountancy: £1,800
• Legal: £1,000
• Office (home office allowance): £500
• General: £2,000

Total expenditure: ~£43,650.

R&D as percentage of total: 34,150 / 43,650 = 78% → ERIS applies.

ERIS calculation:

• Qualifying R&D: £34,150
• Enhanced expenditure: £34,150 × 1.86 = £63,519
• Surrendered loss: lesser of trading loss + enhanced or 186% of qualifying = limited to £63,519 in this case
• Payable credit: 14.5% × £63,519 = £9,210

That's £9,210 paid by HMRC into the company's bank account, typically within 8-12 weeks of submitting the CT600 with R&D claim. Tax-free at company level (it's a credit, not income).

How to file the claim

Pre-submission (before filing CT600)

1. Complete the Additional Information Form (AIF). From August 2023, all R&D claims require a separate AIF submitted alongside the CT600. The AIF includes:
   • Project descriptions for each R&D project (typically 200-500 words each).
   • The technical advance you sought.
   • The technical uncertainties you faced.
   • The competent professional's identification.
   • Cost breakdown by category.
2. Pre-notify HMRC of the claim (only required for first-time claimants or claimants who haven't claimed in 3+ years). Submit a Claim Notification Form within 6 months of the end of the accounting period.

Submission

1. File the CT600 with the R&D credit calculation in the relevant boxes.
2. Submit the Additional Information Form alongside.
3. Submit the Claim Notification Form (if required) before filing CT600.
4. HMRC processes within 8-12 weeks (sometimes longer if they raise enquiries).

Common HMRC enquiries

Enquiry	Founder response
"Provide more detail on the technical uncertainties."	Project-by-project breakdown of what was unknown, what trial-and-error was needed, why a competent professional couldn't have just known the answer.
"Quantify the founder's time on R&D."	Timesheets, GitHub commit history, or project log.
"Are these activities R&D or routine development?"	Distinguish between novel sub-problems (qualifying) and routine integration (not qualifying).
"Provide invoices for subcontractor R&D work."	Standard documentation.

Specialist firms vs DIY

The R&D tax credit consultancy industry charges 15-30% of the claim as a fee. For a £20k claim, that's £3-£6k. It's a real industry that built up around the perceived complexity of the rules.

For a typical solo SaaS claim, you can DIY in 2-3 days of careful work:

1. Identify the qualifying R&D projects (1 day).
2. Quantify costs by category (1 day).
3. Draft the Additional Information Form (1 day).
4. Submit alongside CT600 (1 hour).

If your accountant is comfortable with R&D claims (most are), they can handle it for £500-£1,500. That's a fraction of specialist firm fees and usually sufficient for a clean claim.

If your claim exceeds £100k or you have complex subcontractor arrangements / international R&D / merger transactions, specialist support pays off. Below that, DIY or accountant-handled is the right move.

5 mistakes UK SaaS founders make with R&D credits

1. Not claiming because they think they don't qualify. A solo founder building a non-trivial product almost always has 1-3 qualifying R&D sub-projects per year.
2. Pure-dividend pay structure with no salary. This blocks the founder-time claim. Take a small PAYE salary to unlock the claim.
3. No timesheets / no project log. HMRC enquiries focus on quantification of founder time. A monthly time-percent estimate written down is sufficient evidence.
4. Claiming routine development as R&D. "Built a website" or "added Stripe" doesn't qualify. Resolve uncertainty in the technical sub-problems specifically.
5. Missing the Additional Information Form. Since August 2023, the AIF is mandatory. Submitting CT600 without it leads to claim rejection.

30-min ship-it: prepare your first R&D claim

Step 1 (10 min): Identify qualifying projects
  - List 2-4 sub-problems you solved this year that involved trial-
    and-error or genuine technical uncertainty.
  - Write a 1-line description of each: what was unknown, what was
    found.

Step 2 (5 min): Estimate time spent
  - Founder time on R&D activities (rough percentage by month).
  - If subcontractor was used, hours and dates.

Step 3 (10 min): Quantify costs
  - Salary + employer NIC × R&D % = founder time cost.
  - Subcontractor invoices × 100%.
  - Cloud spend × R&D % (test environments only).
  - Software/data × R&D %.

Step 4 (5 min): Decide route
  - DIY (your accountant's comfort: yes/no).
  - Accountant-led (£500-£1,500 fee).
  - Specialist firm (only if claim >£100k).

Step 5 (5 min): Set CT600 calendar
  - 6 months before period end: pre-notify HMRC if first claim.
  - At year-end: gather full cost evidence.
  - With CT600: submit AIF alongside.

Total time to scope: 30 minutes. Time to full claim: 2-3 days DIY or 1 day with accountant.

Cross-link to other UK SaaS founder reading

• UK SaaS Companies House CS01 walkthrough 2026
• UK indie hacker founder taxes 2026 — director's loan, dividend allowance, MTD ITSA
• UK SaaS accounting reference date 2026 — Form AA01 walkthrough
• UK SaaS VAT registration 2026 — voluntary vs threshold

CTA — get the latest free report

R&D tax credits are real money on the table for indie SaaS founders. So is the rest of UK compliance. The latest free report on a UK SaaS opportunity goes deep on data, competitors, and execution — read it free at ideastack.co/reports.