Definition
Technology Readiness Level, abbreviated TRL, is a nine-point scale that describes the maturity of a technology, originating from NASA in the 1970s and now widely used by Innovate UK, the European Commission and industry. TRL 1 represents basic principles observed and TRL 9 represents actual system proven in an operational environment. The scale is not statutory in UK tax law but is sometimes useful in R&D tax relief narratives to position where qualifying work sits on the development pathway.
How HMRC defines it
HMRC does not use TRL as a statutory test for R&D tax relief, but the scale is compatible with the BIS Guidelines' view that R&D can occur across discovery, development and late-stage engineering. CIRD81300 refers generically to the range of activity covered. Innovate UK applies TRL formally as part of competition eligibility, which can be relevant where grants interact with a claim.
Practical example
A deep-tech SME describes its current project as moving from TRL 4 to TRL 6, covering component validation in a relevant environment through to system demonstration in a relevant environment. The narrative uses TRL as a shorthand for the work's maturity, while the underlying R&D test is still the BIS Guidelines' advance-and-uncertainty criterion.