In plain English
Scientific or technological uncertainty exists where a competent professional cannot readily establish whether a scientific or technological result is feasible, or how to achieve it in practice, using available knowledge. It is different from uncertainty about demand, cost or a team’s familiarity with established methods.
What does the term mean?
The issue is what a competent professional in the relevant field could establish from available knowledge. A team’s lack of familiarity with an existing technique is not enough. Neither is uncertainty about whether customers will buy the product.
DSIT’s guidelines, reproduced in CIRD81910, distinguish this technical uncertainty from matters that a professional could readily resolve. They also recognise that uncertainty can concern how a result is achieved in practice, not just whether it is theoretically possible.
Not every difficult problem is technical uncertainty
| The difficulty | What to examine |
|---|---|
| A team has never used a standard tool | Could established documentation or ordinary professional knowledge supply the answer? |
| A deadline is difficult to meet | Is the obstacle simply time or resources, rather than scientific or technological feasibility? |
| Known components behave unpredictably together | Could a relevant professional readily work out their combined behaviour, or was an investigation needed to resolve a genuine system uncertainty? |
What is system uncertainty?
This concerns the combined behaviour of a system, even where its individual components are understood. Complexity alone is not sufficient: assembling components using established methods does not automatically create qualifying uncertainty. The question is whether their combination presents a problem that cannot readily be worked out by a competent professional.
How to explain it in your project
As a practical writing aid, complete three statements in your own words: “We knew…”, “We could not establish…” and “We investigated by…”. Then support that account with the actual technical record. Avoid simply labelling the whole project “challenging” or copying another company’s narrative.
For example, specify the behaviour you could not predict, the established approach considered, why that approach was insufficient and what your tests examined. These are prompts for an evidence-led explanation, not a formula that guarantees eligibility.
Read what counts as R&D for tax purposes to place this term within the wider qualification test. Finding uncertainty alone does not establish that every activity or cost in the project qualifies.
For help connecting the technical evidence to a claim, explore our R&D tax relief service.
Check the detail
Sources & scope
United Kingdom. This entry uses the 2023 DSIT guidelines, applicable to accounting periods beginning on or after 1 April 2023. Earlier periods require the earlier guidance. It explains the activity definition, not relief rates or a complete claim assessment.
This is an InnoFund explanation, not official guidance or advice on a particular claim. The facts, relevant law and applicable scheme rules must be considered together.
Sources checked: 5 September 2026. This is separate from expert sign-off.
- DSIT guidelines in HMRC’s manual
CIRD81910, paragraphs 13–14 and 29–30
- HMRC: check if you can claim R&D tax relief
Scientific or technological uncertainty
- HMRC: identifying qualifying R&D activities
GfC3, part 4