Although the two words "attachment" and "enclosure" often are used interchangeably in many business letters, they are both different methods of including items within a business letter. For some organizations, such as the government, the use for each is delineated by the correspondence sent, while for others, either use is acceptable.
An attachment is a document that is part of the business letter. It adds or further describes the information within the letter. Some examples include a spreadsheet that provides a visual explanation of financial billing or forecasts, a chart that gives a graphic view of the business trends or a budget. When sending an attachment, include the word, “Attachment” on the bottom right side of the letter with a semi-colon and the number of the attachment, or you could add in the body of the letter that the item is attached.
An enclosure is a document that is in addition to the business letter. It can stand alone as its own document and does not require the business letter to explain what the document is or how to interpret it. When sending an enclosure in a business letter, place the letters “Enc” with a semi-colon or write the word “Enclosure” at the bottom of the letter on the left-hand side. Then put the name of the document. This alerts the reader that a second document is included in the correspondence.
In some situations, there is no method available to differentiate between an attachment and an enclosure. One of these situations occurs when you are sending a business letter by email. Because there is no physical item in which to place an enclosure, and email is a form of electronic transmission, all documents sent be email become an attachment. The attachment is added to the email as a downloadle item that is sent with the body of the email.
There may be rules in place for the use of attachments and enclosures in certain federal government branches. For example, the U.S. geological survey manual, in the correspondence handbook, describes how to handle an attachment and an enclosure when sending correspondence to this government department. According to the handbook, you send an item as an attachment when the correspondence sent is a memo, while if the correspondence is a letter, you will use the word enclosure for additional documents.