They are less formal than letters but should maintain a professional, succinct style. Suppose, for instance, that you were writing to request authorization and funding for a business trip. If readers have a question or problem, they want to know the answer or solution immediately—if readers want more information, they can continue reading.
Business memos are designed to accommodate busy readers who want to find the information they need from the memo quickly and easily. This may be the single most important guideline about the structure and content of memos.
To achieve such a style, use short, active sentences. Readers may also want to get a sense of your professional ability and judgment. Often, the purpose of a business memo is twofold: to identify a problem and propose a solution.