Originality Reports should usually be ready within 15 minutes. However it may take up to 24 hours during peak times such as the middle or the end of semesters when many papers are being submitted to Turnitin. Plan accordingly when working on a deadline.
If an instructor allows multiple submissions on a Turnitin assignment there is a 24-hour waiting period between the each submission. This delay allows resubmissions to correctly generate without matching to a student's previous draft.