Parallel proceedings, or concurrent proceedings, are multiple legal actions that are being heard concurrently by separate courts and which share one or more parties and issues. In fact, for multiple cases to be considered parallel proceedings, they must be essentially identical claims filed in two distinct courts, whether they be a domestic court, foreign court, tribunal, or some other judicial forum.
For example, parallel proceedings can happen when two claims stemming from the same set of facts are filed against a single defendant, one as a criminal case brought by the government and a second as a civil action brought by a private plaintiff.
Parallel proceedings can also involve foreign courts, and as the number of options for legal recourse in international disputes has risen, parallel proceedings have become more common. Oftentimes this is caused by the inability of courts, both in the U.S. and internationally, to consistently enforce cross-border judgments, and so necessitating the filing of similar claims in a different forum since the decision of one court may not be recognized or enforced by another court.