Extrinsic evidence is material used by a court that comes from outside the wording of a document or statute, to help interpret or apply it. It typically includes surrounding circumstances, background facts, prior negotiations, conduct of the parties, and industry practice, as opposed to the “four corners” of the written instrument itself. In contract law across England and Wales, Scotland, Northern Ireland and Ireland, extrinsic evidence is frequently considered when construing ambiguous terms, identifying the factual matrix, or implying terms, but is generally not admissible to contradict clear, unambiguous wording. The parol evidence rule and its recognised exceptions structure this analysis in common law jurisdictions. In statutory interpretation, UK and Irish courts may use extrinsic aids such as Hansard, Law Commission reports and explanatory notes, subject to principles developed in case law (for example Pepper v Hart in England and Wales). The concept is largely a descriptive one rather than a single codified definition, but it is embedded in evidence law, contract interpretation and construction of deeds, wills and commercial instruments throughout the UK and Ireland.