Write or type “Enclosure” followed by the name of the document or content attached. If you've included more than one document, use the plural “Enclosures” and indicate the number of enclosures afterward. The number should either follow a colon or be surrounded in parentheses.
Formally, you would refer to the enclosed items in the body of your letter followed by (enclosed) and then, under the signature at the end of the letter you'd write "Enclosures (x)" where x is the number of enclosures.
On a paper business letter, you often include the CC line underneath your signature, either above or below any enclosures line. Here are the various abbreviations you can use to note carbon copy on printed business letters: cc: c.c.
An enclosure in a cover letter is a list of any additional documents you've included in your application. Typical enclosure documents include letters of recommendation, certificates, a portfolio, work samples, or written tests associated with the job application.