Compulsory Counterclaim in Iranian and the U.S Law.

In U.S there are two types of counterclcompulsory and permissive.In the first one the defendant must submit all the claims arisen out of the transaction or occurrence that is the subject matter of the claimant's claim as counterclaim otherwise his claims would be the subject of res judicata.In Iran by the wording of the article 141 of Civil Procedure submitting the claims arisen out of the same occurrence or transaction or the claims that have complete connection with the main claim as a counterclaim is permissive.Most of commentators view the expression “the same cause” in aforementioned article as unnecessary and useless.Since the reason for consolidation of claims is to avoid conflicting decisions on the same matter and there might be claims arisen out of the same occurrence or transaction still have no connection together. But it seems that above-mentioned expression has an important function.Because making decision on every claim is a consequence of the decision about the occurrence and transaction of which the claim is arisen out.So if claims arisen out of the same occurrence or transaction are submitted in separate cases, that might lead to conflicting decisions.so these type of counterclaims should also be compulsory in Iran.