Pennsylvania Writ to Join Additional Defendants is a legal document that is used in Pennsylvania to add additional defendants to a lawsuit or other legal proceeding. It is a type of legal process known as joiner. This document is used to notify the court that the plaintiff is adding additional defendants to the case, and it must be filed in the court in which the original action is pending. There are two types of Pennsylvania Writ to Join Additional Defendants: permissive and compulsory. Permissive joiner allows the plaintiff to join additional defendants if they have a claim arising out of the same transaction, occurrence, or series of transactions or occurrences as the original claim or if the additional defendants are liable for all or part of the plaintiff's claim. Compulsory joiner is used when the defendant has a right to join the additional defendants in the lawsuit, even if they do not have a claim related to the original claim. The court is then required to join the additional defendants to the lawsuit.