Background and Aim: In the Iranian legal system, international commercial custom in the hydrocarbon industry plays a significant complementary role in determining and interpreting the consideration in oil contracts. The historical evolution of customary mechanisms for pricing and quality assessment—from the era of the Seven Sisters to modern futures-based financial instruments—illustrates the dynamism of these standards. This study aims to examine the validity and function of custom in interaction with Iranian legal rules and the principles of Imamiyyah jurisprudence in resolving ambiguities related to consideration.

Materials and Methods: This research is of theoretical type and the research method is descriptive-analytical and the method of data collection is library and has been done by referring to documents, books and articles.

Findings: An analysis of judicial practice shows that commercial custom has a decisive practical role in areas such as the time and place of transferring consideration, allocation of price-related risks, and assurance of product quality. In Imamiyyah jurisprudence, principles such as sīrat al-‘uqalā, al-ma‘rūf ka-l-mashrūṭ, and the doctrine of contractual intent (taʿbiyyat al-‘uqūd li-l-quṣūd) provide a solid foundation for recognizing and enforcing customary norms.

Ethical Considerations: In order to organize this research, while observing the authenticity of the texts, honesty and fidelity have been observed.

Conclusion: The findings indicate that alignment between customary standards and both Islamic jurisprudential foundations and domestic legal principles enhances stability, predictability, and legal security in oil contracts, thereby contributing to the development of Iran’s energy law system.