R&D Tax Relief for Engineering Firms: Which Projects and Costs Qualify

Engineering is one of the most R&D-intensive sectors in the UK — yet many engineering firms either under-claim or miss R&D tax relief for engineering firms altogether, because the everyday work of solving hard technical problems doesn't always feel like "research". If your team is developing new or improved products, processes, materials or systems and hitting genuine technical unknowns along the way, there's a good chance some of that work qualifies.

This guide sets out which engineering projects and costs qualify, how the current merged scheme works, and the sector-specific pitfalls that trigger HMRC enquiries.

What counts as R&D in engineering

The tax definition of R&D is the same across every sector, and it's stricter than the everyday meaning. To qualify, a project must seek an advance in science or technology by resolving scientific or technological uncertainty — uncertainty that a competent professional in the field couldn't readily resolve. This is set out in HMRC's manual at CIRD81900, which reproduces the government Guidelines on the meaning of R&D.

Two tests matter for engineering claims:

• The advance must be in the field, not just for your business. Reinventing something a competent engineer could look up isn't an advance — even if it's new to you.
• There must be genuine technological uncertainty. If the outcome was readily deducible by a competent professional, it's routine engineering, not R&D.

For a fuller walk-through, see our guide to qualifying R&D activities under HMRC's guidelines and how to evidence technological uncertainty.

Engineering projects that typically qualify

The work most likely to qualify usually involves pushing beyond established methods:

• Developing new or significantly improved products where performance targets can't be met with off-the-shelf design.
• Designing bespoke tooling, jigs or fixtures to achieve tolerances or throughput that existing equipment can't.
• Process and automation development — integrating systems, robotics or control software where the integration itself is uncertain.
• New materials or treatments — trialling composites, coatings or alloys where behaviour under real conditions is unknown.
• Prototyping and testing to resolve a specific technical uncertainty (as opposed to routine iteration or cosmetic changes).
• Scaling a process from lab or bench to production where the scale-up introduces new engineering problems.

What doesn't qualify

Just as important is knowing where HMRC will push back:

• Routine engineering applying existing techniques with a predictable outcome.
• Aesthetic or cosmetic changes with no technological advance.
• Simply assembling known components in a known way.
• Work after the uncertainty is resolved — once the technology works, the remaining production and commercial activity falls outside R&D.

Which costs you can claim

Once you've identified the qualifying project, you claim a proportion of these cost categories, apportioned to the R&D:

• Staff costs — gross salaries, employer's NIC and pension for engineers, technicians and supervisors doing or directly supporting the R&D. Usually the largest part of an engineering claim.
• Subcontractors and externally provided workers — where you contract out qualifying work or use agency staff, subject to the current subcontracting rules under the merged R&D scheme.
• Consumables — materials, components and utilities (power, water, fuel) actually consumed or transformed in the R&D, including materials used to build prototypes.
• Software used directly in the R&D, apportioned where it's also used for non-R&D work.
• Data and cloud computing — a qualifying category since April 2023, relevant to simulation, modelling and test-data-heavy engineering. See our guide to cloud computing costs in R&D claims.

A common engineering trap: prototypes built to test a technical uncertainty can qualify, but a prototype you then sell as a commercial product needs careful treatment — the consumable cost may be restricted once it's not "consumed" in the R&D.

How relief is calculated under the merged scheme

For accounting periods beginning on or after 1 April 2024, most companies claim under the single merged R&D scheme, which gives a 20% above-the-line expenditure credit on qualifying costs (taxable, so the net benefit is lower after Corporation Tax).

Loss-making, R&D-intensive SMEs get a better deal under the Enhanced R&D Intensive Scheme (ERIS): if your qualifying R&D is at least 30% of total relevant expenditure (the threshold for periods beginning on or after 1 April 2024, per CIRD123000), you can claim a more generous payable credit. Many specialist engineering SMEs — where R&D dominates spend — fall into this bracket, so it's worth checking your intensity ratio before defaulting to the merged scheme.

How to make a robust engineering claim

Engineering claims stand or fall on evidence. To protect yours:

1. Identify the uncertainty, not the project. Name the specific technological problem your competent professionals couldn't readily solve, and the advance sought.
2. Keep contemporaneous records — design iterations, test logs, failure analysis, timesheets linking staff to R&D.
3. Complete the Additional Information Form. Every claim now needs a completed AIF with a technical narrative and cost breakdown, filed before or with your CT600.
4. Reconcile your figures across the AIF, the technical narrative and the tax return — mismatches are a leading enquiry trigger.

For worked examples of how this plays out in practice, see our engineering firms R&D relief case studies.

Frequently Asked Questions

Do engineering firms qualify for R&D tax relief?

Yes — engineering is one of the most common qualifying sectors. The work must seek an advance in science or technology by resolving technological uncertainty a competent professional couldn't readily overcome. Routine design and assembly don't qualify, but developing new products, processes, tooling or materials where the outcome is genuinely uncertain often does. We publish sector guides for other R&D-intensive fields too — see manufacturing & advanced materials and life sciences & medtech.

What engineering costs can I claim R&D relief on?

Staff costs, qualifying subcontractor and externally provided worker costs, consumables (materials and utilities consumed in the R&D, including prototype materials), software used in the R&D, and data and cloud computing costs. Each is apportioned to the qualifying activity.

Can prototype costs be claimed?

Materials consumed building a prototype to resolve a technical uncertainty can usually be claimed. But if the prototype is later sold as a commercial product, the consumable cost may be restricted because it wasn't ultimately "consumed" in the R&D — this needs careful treatment.

Which scheme applies to engineering companies now?

For accounting periods beginning on or after 1 April 2024, most companies use the merged R&D scheme (a 20% expenditure credit). Loss-making SMEs whose R&D is at least 30% of total expenditure may instead claim the more generous ERIS.