The insurance contract, as one of the most important risk management tools, is based on the principle of good faith. This principle requires that the parties to the contract, especially the insured, provide complete and accurate information about the subject of insurance. Failure to provide complete information can have significant effects on the validity of the insurance contract. This article conducts a comparative study of the effect of failure to provide complete information on the validity of the insurance contract in Iranian and English law. In Iranian law, the obligation to provide information is regulated based on Article 190 of the Civil Code and Article 14 of the Insurance Law of 1316. In this system, the primary responsibility for providing information lies with the insured, and failure to provide complete information can lead to the cancellation of the contract. In English law, the obligation to provide information is regulated based on the principle of good faith and the Marine Insurance Act of 1906 and the Insurance Act of 2015. In this system, both the insured and the insurer are obliged to observe the principle of complete good faith, and the mere failure to disclose sufficient information is sufficient to cancel the contract. This comparative study shows that both legal systems emphasize the importance of the principle of good faith and the obligation to provide complete information, but there are differences in their approaches. In Iranian law, rescission of the contract requires proof of the insured’s fault, while in English law,