What document formally initiates a civil lawsuit in Illinois?

In Illinois, the document that formally initiates a civil lawsuit is the complaint. This document sets forth the plaintiff’s allegations against the defendant and outlines the basis for the court's jurisdiction, the legal claims being made, and the relief sought by the plaintiff.

The complaint is essential because it serves to notify the defendant of the claims being brought against them and the grounds for those claims. It acts as the starting point of the litigation process, allowing the court to understand the nature of the dispute and the legal issues involved.

While the summons, petition, and notification letter have different functions in the legal process, they do not serve as the primary document to initiate a civil lawsuit. The summons is typically issued alongside the complaint but primarily serves to notify the defendant of the lawsuit and compel their appearance in court. A petition may be relevant in certain types of legal proceedings, often specifically in family law or probate cases, but is not the standard document for starting a civil lawsuit. A notification letter, while potentially useful for communication, does not hold any formal legal weight in initiating a lawsuit.