Which document serves as official notification of a legal action against a defendant?

The document that serves as official notification of a legal action against a defendant is the summons. A summons is a legal document issued by a court that informs an individual that they are being sued or are required to appear in court. It is an essential part of the legal process, as it formally notifies the defendant of the claims being made against them and outlines their obligations, including the timeframe within which they must respond.

In the context of legal proceedings, a summons provides the necessary jurisdiction to the court over the defendant and ensures that due process is upheld by giving the defendant a fair opportunity to be heard. It is delivered alongside the complaint, which contains the details of the allegations.

Other documents mentioned, such as a subpoena, serve different purposes, such as compelling a witness to testify or produce evidence in a legal case. A supporting affidavit is a written statement confirmed by oath, often used to support motions or other legal documents rather than to notify a defendant of legal actions. An arbitration request initiates arbitration, an alternative dispute resolution process, rather than a court action, and does not serve as notification of a legal action against a defendant. Thus, a summons is clearly the correct choice as it explicitly relates to notifying a defendant of pending legal proceedings.