Four Parts:Sample MemosPreparing to Write Your Business MemoMaking Language and Formatting ChoicesComposing Your Business MemoCommunity Q&A. A memorandum—usually known as a memo—is a document which is most commonly used for internal communication between coworkers or members of a department. You may need to use a memo as an external method of communication if, for example, you need to communicate with clients or other business associates. You want to make sure that you get it right: that your memo is professional, clear, and aligns with your profession's standards.