One of the requirements of trade in the international arena is the use of documentary credit as a payment instrument. The proper and desirable functioning of the credit requires the governance of specific rules over it so that, while providing certainty for the parties to international contracts, it also ensures speed in commercial transactions. One of the principles governing the credit is the principle of autonomy, which means that the documentary credit contract is independent and separate from the credit-opening contract and the underlying contract. The application of this principle is not absolute, and exceptions apply to it. On the other hand, one of the important issues in the field of credit is identifying the basis of the issuing bank’s obligation towards the beneficiary. Accordingly, it is necessary to examine, on the one hand, what the principle of autonomy and the exceptions thereto are and, on the other hand, how the basis of the issuing bank’s obligation can be justified and how the exceptions to the principle of autonomy affect that obligation. The result of the research confirms that illegitimacy and nullity are not among the exceptions to the principle of autonomy, and only fraud is regarded as a universal exception. Among the existing theories, the theory based on a contract between the issuing bank and the beneficiary is consistent with the principles governing the credit, and the exceptions to the principle of autonomy affect the issuing bank’s obligation.