Definition
Scientific or technological uncertainty exists where knowledge of whether something is scientifically possible or technologically feasible, or how to achieve it in practice, is not readily available or deducible by a competent professional working in the field. It is the central test for research and development under the BIS Guidelines: a qualifying project must seek an advance through the resolution of such uncertainty. Commercial, regulatory or financial uncertainty does not count.
How HMRC defines it
HMRC guidance on technological uncertainty is at CIRD81300 of the CIRD Manual, cross-referenced to paragraphs 12 to 18 of the 2023 BIS Guidelines. HMRC distinguishes system uncertainty, where individual components are known but their integration is not, from component uncertainty and from uncertainty as to the very existence of a solution. All three can support a valid R&D claim.
Practical example
A machine-learning company attempts to predict a specific industrial outcome from streaming sensor data. Published techniques address adjacent problems but none covers the full data pipeline and feedback latency required. A competent professional cannot readily deduce the architecture needed, and iterative experimentation is required. This is genuine scientific or technological uncertainty.