An addendum to a letter, added after the author's signature.
{{quote-book
An addition to a story, play, etc. after its completion.
(quote-journal)
{{quote-book|en|year=2010|author=Maggie O'Farrell|title=The Hand That First Held Mine|publisher=Headline|isbn=9780755308453|page=34
To extend (a letter or another document) with additional remarks.