Lawful issue refers to a person’s legitimate descendants, typically children, grandchildren and further lineal descendants who are recognised by law as such for succession, inheritance and trust purposes. Historically, “lawful issue” usually meant children born within marriage and excluded illegitimate or adopted children, but modern legislation in England and Wales, Scotland, Northern Ireland and Ireland has largely removed discrimination based on birth status and includes adopted children in most succession contexts.The expression is frequently used in wills, settlements, family trusts and older conveyancing documents to identify a class of beneficiaries who take on death, often as “lawful issue of the body”. Its effect is interpreted in light of applicable succession and adoption statutes and case law in the relevant jurisdiction, and, in older instruments, may still exclude illegitimate children unless a contrary intention appears.Although not generally defined in a single statute, the meaning of “lawful issue” has been developed through case law and interpretative legislation concerning wills and trusts. Across the UK and Ireland, usage is broadly consistent, but practitioners should always construe the term contextually and by reference to the date and governing law of the instrument.