According to the APA referencing format, "unpublished" includes manuscripts - in progress, *informally published or submitted for publication.
If the manuscript meets the above criteria, the date will be the year it was completed. If the date cannot be determined, use the abbreviation (n.d.). (no date). Do not add, "in preparation" or "submitted" to the date.
The status of a manuscript is added after the title in square brackets - [Manuscript submitted].
If the manuscript has been accepted for publication, but not yet published, use (in press) as the date.
*Informally published - published via a pre-print archive or institutional repository.