In followup to the post Proper novella format, a reader writes to ask:
What do you do if you are using a novella as part of a short story collection?
If you're including a novella in a collection, then format it essentially like you would a short story.
This, however, begs the question of proper format for a story collection. Different authors do collections in a couple of different ways. The quick-and-dirty way would be to just print out all your stories in normal short story format, then slap a title page (complete with total estimated word count) and a contents page on top of the stack and call it a day. I'm sure plenty of collections have been sold this way (which includes the bonus of allowing the editor to shuffle stories around to her heart's content).
But you might better treat your collection similarly to a novel manuscript. Give it a title page, and thereafter start each story on its own page with the title centered halfway down the page. Adjust the page numbering so that it continues sequentially through the whole manuscript, and does not start over again at 1 for each story. This, especially for a newer writer, will make your collection look more like an intentional book and less like a slapdash pile of stories.
Either way, treat any novella you include in the collection the same as any other story, with chapter headings centered after a skipped line rather than starting on a new page.
Also, don't forget to include, up front or at the end, a list of where each story was previously published. If a story was not previously published, indicate that too. An exception might be if the bulk of the stories in the collection are previously unpublished, in which case you will probably want to refer to your submission in your cover letter as a collection of original (not unpublished) stories.