When you write a business letter, you usually have to follow business formatting protocols. A cover letter is no exception. A point of debate is the use of an enclosure notation at the end of a cover letter. Using the notation still is standard as of 2011, but to decide whether to follow convention, you have to understand why the notation is used.
The primary reason you put an enclosure at the bottom of a cover letter is to alert your recipient as to exactly what the cover letter accompanies. The recipients can look at the enclosure list and compare it to what they've received to ensure that they're not missing anything. If something isn't there that should be, the recipient can contact you and tell you exactly what to resend. A secondary reason is to help your recipient keep your materials together. This becomes extremely important in instances where the recipients may get dozens of similar letters, such as when they're accepting job applications. If materials get scattered and mixed, the recipients can use the enclosure lists to reconstruct each applicant's packet.
Necessity and Technology
By definition, a cover letter introduces other materials, although the materials may be virtually any printed document or small, shippable item. For this reason, a printed cover letter always needs the "enclosure" notation. However, technology is spicing up cover letter and enclosure etiquette. If you send a cover letter via email, you really cannot enclose anything -- the idea of the "enclosure" is that you physically surround the item, as with an envelope. Because of this, an email cover letter that uses attachments should use "attachment" as a replacement for "enclosure."
Although you must indicate enclosures at the bottom of a cover letter, you have some flexibility as to how to do this. The first option is to write the word "Enclosure" followed by a colon and a brief description of the enclosure -- use this if you have only one item enclosed with your cover letter. If you have multiple enclosures, the simplest way to indicate it is to write the number of enclosures followed by the word "Enclosures" -- for instance, "4 Enclosures." You also can write "Enclosures" followed by a colon, then indicate all the enclosures in a numbered list, one enclosure description per line. Alternately, write "Enclosures," followed by the number of enclosures in parentheses, then a colon. Then list a description of the enclosures, one description per line.
In many cases, it is imperative to keep cover letters concise and within a one-page limit. Because the purpose of a cover letter is to introduce what you are sending, some professionals argue that you can omit the "enclosure" indication to save space, provided you clearly indicate all the enclosures in the letter body. This has a disadvantage, however, in that it does not let your recipient identify the enclosures as quickly -- with an enclosure indication, your reader can tell what you've sent in just seconds without actually reading the letter itself.