This study examines the need to revise and reform the Act Mandating the Official Registration of Real Estate Transactions, focusing on the legal status of informal dealings involving immovable property, particularly in terms of their validity or evidentiary admissibility. Adopting a descriptive-analytical methodology, the research conducts a comparative analysis across the legal systems of France, Germany, England, and Switzerland. The central question is: What legal approaches have been adopted in major European jurisdictions concerning informal land transactions? Which approach does the Iranian legal system pursue in its recent Act, and from a normative perspective, which approach should be utilized and what solutions can be prescribed and recommended to the legislator? A comparative study of the subject in European countries depicts that our legislator has pursued the approach of England, Germany, and Switzerland, considering informal land transactions invalid. Nevertheless, the French approach and the theory of non-opposability of informal transactions can better serve the purpose and philosophy of foregoing Act, protecting bona fide third parties, and upholding the contractual parties’ rights, while being more compatible with Islamic law. Furthermore, there exists a significant degree of legal uncertainty and scholarly debate concerning the applicability of the newly enacted Act Mandating the Official Registration of Real Estate Transactions to various dealings -both formal and informal, and in some cases conflicting- that were concluded prior to its coming into force. Particular controversy arises in cases where immovable property has been formally transferred to multiple parties, yet the originating transaction is subsequently declared void for a specific legal reason. A number of judicial bodies, relying on a literal reading of the new statutory provisions, have adopted the view that the law does not extend to transactions concluded prior to its effective date. Conversely, another group of courts has sought to safeguard the legal status of official documents and promote the objectives of the registration mandate, even in relation to pre-existing agreements. The latter interpretation appears more consistent with the legislative intent behind the enactment—namely, the protection of bona fide third parties—and is further supported by the interpretive nature of the new statute, which, in essence, reflects a reaffirmation of the doctrinal framework established under Articles 22 and 46 to 48 of the Real Estate Registration Act. In order to eliminate existing ambiguities and divergent interpretations surrounding the aforementioned legislation, it is recommended that the legislator undertake a comprehensive revision of the law. However, in order to resolve ambiguities and disagreements regarding the Law Mandating Registration, it is suggested that the legislator, by amending and revising Articles 1 and 10 of the Act, accept the theory that informal real estate contracts are not valid against formal transactions (non-opposability), and consider this ruling applicable to past transactions in line with Articles 22 and 46 to 48 of the Registration Act. Pending legislative intervention, it remains incumbent upon the judiciary to pursue a jurisprudential approach to enhance the validity of official instruments.