Although exclusion clauses which appear in the form of limitation clause and nullify clause of liability of commited and they are consequential obligations, but this group of clauses contain all principal obligations. These clauses contain all range of obligations (including the contract and off – contract) and have influenced them and study of these influences in contract law are consequential . Although in jurisprudence under the old theory "impossibility of nullifying of non- existence", acceptance of these clauses is difficult but on clause of acquittance of defects or retiring commitment of husband on future alimony, we can find traces of admission of such clauses. Although in Iranian law, there is no specific act in this area, but there can be find from dispersed sections that legislator except in exceptional circumstances has warranted the accuracy of such clauses, but in English law situation is different, such that in addition to dynamic judgmental procedure in the field of exclusion clauses and existence of variouse cases, the legislator by passing special acts such as "unfair contract terms act 1977" has developed diverse, useful, dynamic and significant rules in these context that study of such acts can be useful for Iranian juristics and legislator.