What is the most common format for a professional memo?

Business memorandums typically have five parts: recipient, sender, date, subject and message. Purdue University's online writing lab and Dummies.com both explain the purpose and format of a memo and offer sample memos.

In a business memo, the top line, or "to" line, states the recipient's full name and job title. A memo can have more than one recipient. The second line, the "from" line, notes the sender's full name and title. The third line notes the complete date. The fourth line is for the subject, a brief but specific statement as to the memo's topic.

The text of the memo follows these four lines. Its language can be informal but should still be business-like. The first paragraph gives an overview of the memo's purpose, the problem being addressed, and the tasks being done to solve the problem. The following paragraphs offer more details to this overview. Long memos may need a summary statement at the end.