Sufficient cause describes a reason or explanation that a court or tribunal accepts as adequate to justify a procedural step not otherwise allowed, such as extending time limits, setting aside a default judgment, or reinstating struck-out proceedings.Across England & Wales, Scotland, Northern Ireland and Ireland, it is a flexible, context‑specific standard rather than a rigid statutory formula. Legislation and rules of court more often use related expressions such as “good reason”, “good cause” or “good and sufficient cause”, with case law clarifying what will be treated as sufficient cause in particular contexts (for example, illness, serious procedural error, or misleading conduct by the other party, but usually not mere oversight or workload).The concept is central to applications for relief from sanctions, motions for extension of time, appeals lodged out of time, and applications to recall or set aside orders. Courts in all four jurisdictions balance the adequacy of the cause against factors such as finality of litigation, prejudice to the other party, compliance culture and the interests of justice. Usage and underlying principles are broadly consistent, though the precise tests and terminology derive from the specific procedural rules and authorities in each jurisdiction.