Submitting an official transcript vs unofficial transcript for postgraduate studies; why the difference?
The primary issue is expediency. It can take time to issue official transcripts. The sooner a candidate has a complete application on file, the sooner it can be evaluated. In addition, most schools that may allow unofficial transcripts generally require an official transcript before matriculation. If it is found that the unofficial transcript doesn't match the official transcript, then that would be grounds to cancel the offer of admission.