In letter of credit transactions, four common letter of credit message formats-MT 700, MT720, MT760 and MT 799-all have their own unique functions and application scenarios. As the standard of electronic opening of documentary credit, MT700 is the main message form of modern electronic opening of credit, which marks the direct opening of credit. MT720 is used in the transfer process of transferable letters of credit. When the beneficiary receives the letter of credit in MT720 format, it means that they become the second beneficiary through transfer, that is, the letter of credit has been transferred once.

MT760 is specially used to send bank guarantee, that is to say, when a guarantee is transmitted in this format, it is usually the confirmation of the guarantee commitment between banks. Finally, MT799 is a free message format between banks, which is mainly used for inter-bank communication and handling the amendment of letters of credit. In this case, if the issuing bank finds that the contents of the letter of credit are wrong, it will communicate with the advising bank through MT799 and amend it by itself. This amendment does not require the beneficiary or the applicant to pay additional fees, because it stems from the issuing bank's own mistakes.

To sum up, these four message formats represent different stages of the life cycle of the letter of credit and different stages of inter-bank cooperation, and play a key role in ensuring the accuracy and efficiency of the letter of credit process. Understanding these differences is helpful to correctly select and use the appropriate message format in actual operation.