Enclosure would normally apply "to" something placed in the sending envelope.
Student or Learner
Please explain me what the difference is between enclosure and attachment with samples.
A letter may include an enclosure; an email may include an attachment.
Attachment, with respect to a printed document, means the item is physically connected to the primary document, often with a staple.
Enclosure means the item is placed in the same envelope or package.
I am not a teacher.