It depends. If you're planning to drop a course and want to stay with your faculty, you can easily do that internally.
If you're planning to drop your faculty, you will have to apply through UAC.
Example: Bachelor of Science/Bachelor of Business WANTING to transfer to Bachelor of Business, you will have to apply through UAC because this course is from the SCIENCE faculty. For a student wanting to drop the Bachelor of Business, internal process (which is quite easy).
For a person doing B.Business/B.International Studies wanting to drop B.International Studies, they can easily do that through internal process because you're still in the BUSINESS Faculty
To see which faculty you're in, go to the student handbook online, but it's normally the proper name of your course. Bachelor of Science/Bachelor of Business. It is normally the first faculty name which faculty you belong in. B.Business/B.International Studies
They know that students would drop one course as some courses @ UTS have a lower ATAR cutoff than the single course. B.Science/B.Business is 85.75, where B.Business is 91.
Either way, both internal and UAC applications are closed now and you will have reapply during the Semester 2 intake of 2014.
I know, tough process.