Add NUS students and staff as guests to my course

Students and staff who wish to audit academic courses can be added as Guest students. They can be added from the People section in Canvas.

Please use their staff or student NUS-IDs (e.g., e0123456) to add.
Select the SIS ID or Login ID option.
Friendly emails and non-NUS email addresses will not work. For non-NUS users, refer to Add non-NUS users to a course.
For academic courses, the guests should be added with the Guest Student role. For other types of courses, other roles are possible.

Do not add students who are supposed to be enrolled officially to a course as guest students.

Guest Student (Observer) role is different permission that the Student role. Observers have limited permissions that allow them to see what is going on in a course, but will not be able to participate in graded assignments.
You will have to remove the guest student role manually from each student (i.e. one-by-one) once they have officially joined the course in Canvas.