Students can upload and overwrite documents through the same assignment. The initial report will be generated in around 15 minutes, whilst subsequent uploads will take 24hrs. Newer uploads will overwrite the original document and therefore will not ‘match’ against each other.
If one assignment is used for drafts and a second assignment is used for the final submission it is important to set the draft assignment to the ‘no repository’ setting so that the later final submission by the student doesn’t match with the earlier assignment.
Turnitin will match documents created by the same upload across different assignments to help highlight possible self-plagiarism of students’ work.