R&D Tax Credits for Engineering Companies
Written and reviewed by the R&D Tax Accountants editorial team. Last reviewed 8 August 2026.
Engineering companies have among the strongest R&D claims in the UK and among the highest rates of unclaimed relief. The reason is a vocabulary problem rather than an eligibility problem: the work is called design, or development, or solving a problem for a customer, and nobody in the business calls it research.
The statutory test does not use the word research in the way a laboratory would. It asks whether a project sought an advance in science or technology and faced uncertainty that a competent professional in the field could not readily resolve. A great deal of ordinary engineering meets that description.
What Counts as Engineering R&D
The qualifying activity is the part of a project where the outcome was genuinely in doubt on technical grounds. Developing a component to a tolerance nobody had achieved with a given material, establishing whether a mechanism could survive a duty cycle, redesigning a system to work within a thermal or weight envelope that had previously made it impossible: each of those is capable of qualifying.
What does not qualify is applying established engineering practice competently. Selecting from known solutions, sizing to standard calculations or adapting a proven design to a new set of dimensions is skilled work without technological uncertainty in the statutory sense.
The project does not need to have succeeded. A development abandoned because the uncertainty could not be resolved still qualifies for the costs incurred before it stopped, which is set out on the R&D tax credits guide.
The Competent Professional Test in Engineering
This test does more work in engineering than in any other sector, and it cuts both ways. The question is whether a competent professional working in the field could readily have resolved the uncertainty using publicly available knowledge and their own expertise.
That standard is higher than novelty to your own team. If the answer was in the literature, in a standard, or in the ordinary experience of a senior engineer in that discipline, the uncertainty was not technological even though your team had to work it out. Equally, if your senior engineers could not say at the outset whether the thing was achievable, and could not find out without trying, the test is met however routine the project looked on the schedule.
The practical consequence is that the person who has to describe the uncertainty is the technical lead, not the finance team. A narrative written from a project plan almost always describes activity rather than uncertainty.
Costs That Dominate an Engineering Claim
Staff time is usually the largest line, and the apportionment behind it is what a compliance check tests first. A round percentage with nothing behind it is a weak claim; time recorded against development activity, or a defensible estimate built from project records, is a strong one.
After that, consumables genuinely consumed in development and testing, and payments to externally provided workers and subcontractors, restricted to 65% where the provider is unconnected. Capital expenditure, the cost of land, and rent, rates and leasing costs are all excluded from this relief.
HMRC sets out the cost categories in its guidance on which R&D costs can be claimed. Engineering companies pursuing grant funding alongside relief will find that route through Innovate UK, and it can affect which scheme applies to which expenditure.