Consolidation of lawsuits may be ordered by a court when two or more lawsuits involving the same or similar parties (plaintiff and defendant), legal issues, and factual issues are pending in the same court or in different courts in the same jurisdiction (state court system or federal court system). If the lawsuits are pending in different courts one case may be transferred to the other court, and the cases consolidated there.

Laws and rules regarding the consolidation—or transfer and consolidation—of lawsuits vary from state to state and in the federal court system.

In New Hampshire, the consolidation of lawsuits is governed by state statutes and court rules. According to Rule 42 of the New Hampshire Superior Court Rules, when two or more actions involving a common question of law or fact are pending before the court, it may order a joint hearing or trial of any or all the matters in issue in the actions; it may order all the actions consolidated; and it may make such orders concerning proceedings therein as may tend to avoid unnecessary costs or delay. This is intended to promote judicial efficiency and reduce the possibility of inconsistent judgments. The decision to consolidate is at the discretion of the court and is typically based on the court's determination that consolidation would serve the interests of justice and judicial economy. If the lawsuits are pending in different courts within the state, a transfer may be ordered to consolidate the cases in one court. The process for transferring and consolidating cases may involve a motion by one of the parties or be initiated by the court itself. Federal courts have a similar rule under Federal Rule of Civil Procedure 42(a), which allows for consolidation when actions involve common questions of law or fact. The decision to consolidate federal cases, like state cases, is discretionary and aims to streamline the litigation process and avoid conflicting rulings.