Answer:
The notation that is made in a formal business letter that contains additional documents in the envelope is:
“Enc.” or “Att.”
Explanation:
"Enc." means "Enclosures," while "Att." means "Attention." These notations draw the attention of the letter recipient to the fact that there are other documents that may be accompanying the business letter. The plural form of the word "Enclosures" is regularly used with the number of enclosures indicated. But if it is one document, then the word "Enclosure" is preferred, indicating that the document is not more than one. When "Attention" or "Att." is used, the documents are listed.
