cover note
noun [ C ] uk/ˈkʌv.ə ˌnəʊt/ us/ˈkʌv.ɚ ˌnoʊt/
(INSURANCE)
law UK specialized暂保单（拿到正式保险单前开具的保险凭据）
a document that is used temporarily as proof that someone is insured until the final official document is available
(LETTER)
US (UK covering note)附函，附信
a short letter that contains information about the thing it is sent with
He sent a sample of his work with a cover note. 他寄去了自己的作品样品，并附上了一封信。