the foreign exchange memo that handling institutions and foreign currency exchange agencies need to keep is required to be kept for 5 years for future reference according to the Guidelines on Foreign Exchange Business under Current Account (22 Edition). These water bills are important records and vouchers in the business, which are used to check the amount exchanged and the information of both parties, so that they can be consulted or processed when necessary. For foreign currency exchange agencies, it is also necessary to pay attention to the rules for the use and preservation of the memo. The foreign currency exchange memo retained by the foreign currency exchange agency should be confirmed by the customer's signature and the seal of the handling personnel, and must be written in triplicate. One copy should be kept by the customer, one copy should be sent to the authorized bank, and the other copy should be kept by the foreign currency exchange agency for bookkeeping.