At first glance the differences between letters and memos may seem negligible. While an obvious difference is that letters are used to communicate with those outside an organization and memos are designed for those within, there are other important distinctions in the way information is conveyed. Because most workers routinely write both letters and memos, knowing the differences between how to format letters and memos is essential to maintaining professionalism and credibility.
Set margins to 1 inch all around for longer letters and 1 ½ inches all around for shorter ones. Sometimes, however, “it is more important to establish a picture frame or blank space surrounding the page of text” according to the authors of Handbook of Technical Writing, in which case modify margins accordingly. Adjust memo margins to 1inch on the top and bottom and 1 ¼ inches on the right and left sides.
Letters may use either full block or modified-block style. If the paper has letterhead, use full block style, aligning all text at the 1 inch left margin. If the paper does not have letterhead, provide your business address and date in a single block; place it and the closing at the beginning of center, aligning the remaining text at the left. On memos, center your department’s name and directly underneath the word "Memorandum", capitalizing both.
If the paper does not have letterhead, include an address block and an inside address. Omit your name from the address block, spell out street and state names, and end with the date. Skip two spaces and begin the inside address. Start with the recipient’s name, title, and address. For memos, headings include the following: to, from, date, and subject, with a colon and one blank space after each. Senders should initial their names.
In a letter, place the greetings two lines below the heading. Greet a specific person and add a colon. Unlike a letter, salutations are not used in memos, which begin by directly stating the purpose of the document instead.
When writing a letter, body paragraphs begin two spaces below the heading. Use single spacing within the paragraph and add two blank spaces between paragraphs. Memos often contain headings and lists, which may use numbers or bullets to summarize main points.
Closing and Signature Block
Close with the words sincerely or cordially yours. Leave four blank lines, and then include your name and honorifics. Below that place your title. Skip two lines for additional information, such as reference initials, enclosures, or copy notations. Memos do not contain a closing or signature.