If you run a digital agency that builds custom software for clients, you have almost certainly wondered whether the work qualifies for R&D tax credits. And you have probably been told it doesn't, because the software belongs to the client, not you.

That advice is half-right and half-wrong. And the wrong half could be costing your agency tens of thousands of pounds.

Here is the truth: R&D tax credits for custom software built for client projects are absolutely claimable, provided the work meets HMRC's definition of qualifying R&D. The ownership of the intellectual property is not the deciding factor. What matters is whether the project involved resolving technical uncertainty that a competent professional in the field could not readily overcome.

This article explains exactly where the line sits, what HMRC looks for, and how to structure a claim that survives scrutiny. We are ICAEW qualified accountants who work exclusively with agency founders, and we see too many agencies leave this money on the table because of a misunderstanding that is now costing them real cash.

What HMRC Actually Means by R&D

Let's start with the statutory test. Under the Corporation Tax Act 2009, qualifying R&D exists when a project seeks to achieve an advance in science or technology by resolving scientific or technical uncertainty that is not readily deducible by a competent professional in the field.

Three conditions must all be met:

  • An advance in science or technology overall, not just for your business or client
  • Technical uncertainty that could not be resolved by a competent professional working in the field
  • A project that attempted to resolve that uncertainty, whether or not it succeeded

Notice what is not in that list. There is no requirement that you own the resulting IP. There is no requirement that the work was speculative rather than client-funded. There is no requirement that the project was internal rather than commercial.

The question is purely technical: did you attempt to solve something that no competent developer could have solved with existing knowledge?

Where Most Agencies Get It Wrong

The most common objection we hear from agency founders goes like this: "We just built a standard CRM for a client. There was nothing innovative about it. We used React, Node.js, and a PostgreSQL database. That's not R&D."

And that is correct. Building a standard CRM using well-understood tools and established patterns is not R&D. You did not resolve technical uncertainty. You applied existing knowledge competently. That is good work, but it is not claimable.

But here is where the same founder often misses the real opportunity. Within that same project, the client asked for a module that could process real-time video feeds from 200 simultaneous sources, extract facial expressions, and generate sentiment analysis within 200 milliseconds. The standard libraries could not handle that load. The existing documentation was contradictory. The team spent six weeks iterating on data pipeline architectures, testing different compression algorithms, and building a custom caching layer that did not exist before.

That six weeks is R&D. The rest of the CRM build is not. And the fact that the client paid for the entire project does not disqualify the R&D element.

HMRC's own guidance is clear on this. The CIRD81900 manual states that work can qualify regardless of whether it is funded by a client, as long as the technical uncertainty exists and the advance is genuine.

The IP Ownership Myth

There is a persistent belief that R&D tax credits require the claimant company to own the intellectual property generated by the project. This is not correct for the SME R&D tax credit scheme.

Under the SME scheme, the claimant must be the company that carried out the R&D. That company must also bear the financial risk of the R&D expenditure. But "bearing the financial risk" does not mean you cannot charge the client for the work. It means you must be the entity that pays for the staff time, subcontractors, and materials involved in the R&D activity.

In practice, this works perfectly well for most agency-client relationships. Your agency employs the developers, pays their salaries, covers the software licences, and invoices the client for the completed work. You bear the cost of the R&D activity. The client pays for the outcome.

Where it gets complicated is if the contract transfers the financial risk to the client through a cost-plus arrangement or a time-and-materials agreement where the client reimburses your costs directly. In those cases, the risk may sit with the client, and the claim would belong to them, not you. But for a standard fixed-price or milestone-based project, the risk sits with you, and the claim is yours to make.

What Qualifies as Technical Uncertainty in Software

This is the practical question that determines whether your claim will succeed or fail. HMRC does not accept "we built something new for our client" as sufficient. The advance must be in the underlying science or technology, not just in the application of existing technology to a new commercial context.

Examples that typically qualify for R&D tax credits custom software agency claims:

  • Developing a novel algorithm to process unstructured data at scale where existing libraries could not handle the volume or accuracy requirements
  • Building a real-time rendering engine for 3D visualisations where off-the-shelf solutions produced unacceptable latency
  • Creating a custom machine learning model that required adapting fundamental approaches because standard architectures failed on the specific data set
  • Designing a distributed system architecture to handle 10x the throughput of any existing reference implementation, requiring novel approaches to data sharding and consistency
  • Developing a custom compression algorithm for high-resolution medical imaging where existing standards produced unacceptable quality loss

Examples that do not qualify:

  • Building a standard e-commerce website using Shopify or WooCommerce, even with heavy customisation
  • Integrating third-party APIs using their documented methods
  • Applying standard design patterns to build a mobile app
  • Migrating a database from one platform to another using standard tools
  • Building a website with a custom CMS where the underlying technology choices are well-established

The line can be fine. A project that looks like routine development on the surface may contain genuine R&D activity underneath. The key is to identify the specific technical uncertainties that your team faced and the work they did to resolve them.

How to Structure Your Claim

If you have identified qualifying R&D activity within client projects, the next step is to prepare your claim properly. HMRC has become significantly more rigorous in recent years. Claims that lack technical justification or are supported by vague descriptions are being rejected at increasing rates.

Here is what a strong claim looks like:

1. Identify the Technical Uncertainty

Start with a clear statement of what was not known at the start of the project. "We did not know whether it was possible to process 200 simultaneous video streams with sub-200ms latency using the available hardware" is specific and testable. "We needed to build a better system" is not.

2. Describe the Competent Professional Test

Explain why a competent developer or engineer in your field could not have resolved the uncertainty using publicly available knowledge. Reference specific documentation, libraries, or approaches that were tried and found insufficient. This is the core of the claim. Without it, you have nothing.

3. Document the Work Done

This is where most agencies fall down. You need contemporaneous records of the R&D activity: project notes, technical specifications, sprint retrospectives, test results, internal emails discussing technical problems, Slack conversations about alternative approaches. HMRC will not accept a retrospective narrative written after the fact. They want evidence that the work happened when you say it did.

4. Separate R&D Costs from Non-R&D Costs

You cannot claim for the entire project budget. You need to isolate the staff time, subcontractor costs, and materials that were specifically consumed by the R&D activity. This requires timesheets or project tracking that distinguishes R&D hours from routine development hours.

Most agencies we work with use a simple approach: tag specific tasks or sprints as R&D in their project management tool (Jira, Asana, Monday.com), then pull the hours from there. If you are using Xero or QuickBooks for time tracking, you can create a separate R&D project code.

The Numbers: What Is It Worth?

Let's make this concrete. Suppose your agency is a 15-person digital agency turning over £1.2m per year. You have a team of eight developers. Over the course of the year, three client projects contained genuine R&D activity totalling 400 developer days, or roughly two full-time equivalent developers for 10 months.

At a fully loaded cost of £450 per developer day (salary, employer NI, pension, software, overheads), your qualifying R&D expenditure is £180,000.

Under the SME R&D tax credit scheme, you can enhance that expenditure by 186% for 2025/26 claims. That gives you a qualifying deduction of £334,800 against your taxable profits. If your agency pays corporation tax at 19%, that reduces your tax bill by £63,612. If you are loss-making, you can surrender the loss for a cash payment of up to 14.5% of the enhanced expenditure, which would give you roughly £48,500 in cash.

That is real money. And it is money that most agencies leave on the table because they assume client-funded work does not qualify.

The Risks You Need to Know

R&D tax credit claims are high-value, which means they attract attention. HMRC opened over 90,000 compliance checks on R&D claims in 2023/24, and the rejection rate has climbed sharply.

The biggest risk for agencies is overclaiming. If you claim for the entire project cost when only a portion was genuinely R&D, HMRC will reject the claim in full and may open a wider enquiry into your corporation tax returns. The penalties for careless or deliberate inaccuracies can be significant.

The second risk is inadequate documentation. If HMRC asks for evidence of the technical uncertainty and you cannot provide contemporaneous records, they will disallow the claim. You cannot reconstruct technical uncertainty after the fact. It either existed at the time or it did not.

The third risk is the subcontractor rules. If you use subcontractors to perform R&D work, the rules are different. Under the SME scheme, you can claim for subcontractor costs only if the subcontractor is an individual or a partnership. Payments to limited company subcontractors are not qualifying expenditure. This catches many agencies out.

Should You Claim Through the RDEC Scheme Instead?

If your agency is large enough that it no longer qualifies as an SME (typically more than 500 employees or turnover above €100m), you will claim under the RDEC (Research and Development Expenditure Credit) scheme instead. RDEC is a taxable credit worth 20% of qualifying expenditure, and it is less generous than the SME scheme for most agencies. But the qualifying criteria are similar, and the documentation requirements are equally strict.

Most agencies reading this will be SMEs, so the SME scheme is the relevant one. But if you have grown significantly or are part of a group structure, check your status before claiming.

Practical Steps to Take Now

If you think your agency has qualifying R&D activity in client projects, here is what to do before your next year-end:

  1. Review your current and recent projects. Look for work that involved genuine technical uncertainty. Talk to your technical leads. They usually know exactly where the hard problems were.
  2. Start documenting now. If you have ongoing projects that involve R&D activity, set up a system to track the time and record the technical challenges as they happen. A simple shared document updated weekly is better than nothing.
  3. Get professional advice. R&D tax credit claims are not DIY territory for agencies. The rules are complex, the documentation requirements are specific, and the HMRC scrutiny is real. Work with accountants who understand both the tax legislation and the agency context.
  4. Do not assume past claims are impossible. You can amend corporation tax returns for up to two years after the filing deadline. If you had qualifying R&D activity in the last two years that you did not claim for, you can still make a claim.

At Agency Founder Finance, we specialise in helping agency founders identify and claim R&D tax credits they are entitled to. We have seen claims worth over £100,000 for agencies that had never considered client-funded work as qualifying. If you want to know whether your agency has a claim, get in touch. We will tell you honestly whether the work qualifies, and if it does, we will help you structure the claim properly.

The key takeaway is simple: R&D tax credits are not just for labs and pharmaceutical companies. They are for any business that resolves technical uncertainty, including agencies building custom software for clients. The question is not who owns the IP. The question is whether your team solved something that nobody had solved before.