In this article, we explain what an enclosure is and how to cite one, and we provide an example of an enclosure in a business letter. Include an enclosure after the formal closing at the end of your letter.If you have a single enclosure, note it beside the colon. This instruction provides naval afloat command safety standards and precautions necessary to carry out the program established in reference (a). For example, a letter that simply states "Enclosed is correspondence of John.