memo vs letter A memorandum or shortly known as a memo is a precise official note, used to inform, direct or advise the members within the same organisation. However, the business deals with a number of external parties such as customers, clients, suppliers, government agencies, manufacturers, societies, etc. for which a different tool of communication is used, called as a business letter. A letter refers to a brief message sent by the company to the person or entity, which are outsiders.
