An oath is a formal promise to tell the truth or perform a duty, made before a court or authorised person, usually invoking a deity or sacred text. It is used in all UK and Irish jurisdictions when giving evidence (for example, as a witness, deponent or interpreter) and when assuming certain public or professional offices (such as judicial or parliamentary oaths).In England and Wales, Scotland and Northern Ireland, oaths in court proceedings are governed principally by the Oaths Act 1978 and related rules of court. In Ireland, oaths are regulated by the Statutory Declarations Act 1938 and court rules. In all four jurisdictions, a person with no religious belief or who objects to taking a religious oath may instead make an affirmation with the same legal effect.A false statement made on oath may constitute perjury or a related offence, with significant criminal penalties. Only specified office‑holders (such as solicitors, commissioners for oaths, notaries public and certain court officials) are authorised to administer oaths. The form of words may vary, but the essential legal feature is the solemn undertaking, creating a binding obligation to tell the truth or faithfully perform the sworn duty.