Which document must be served on every party involved in a case?

The document that must be served on every party involved in a case is an order stating that service is required. This document is essential because it formalizes the legal obligations of the parties involved, ensuring that everyone is notified of critical developments in the case. It typically outlines what the parties need to be informed about and allows them to prepare for proceedings accordingly. Proper service of this order is crucial for maintaining fairness and transparency in the legal process, as it enables all parties to be aware of the actions being taken.

In contrast, a verbal agreement between parties lacks the formalization and legal enforceability required in judicial matters. A petition for a special hearing pertains to specific procedural requests but does not necessarily involve all parties in the same way the order does. Similarly, a complaint filed in a different jurisdiction is not relevant to the case at hand and does not serve the purpose of notifying parties involved in the current matter. Therefore, the requirement for serving an order stating that service is required is fundamental to ensuring all parties are united in the legal proceedings.