Canvas now allows instructors and TAs to submit an assignment on behalf of a student. This is useful when you receive an assignment from a student electronically (such as through email or flash drive) and you can still use the Canvas tools (Speedgrader) to grade and submit feedback for the assignment.

To do this, open the Student Detail tray in the grade book and select the Submit for Student button.

For step-by-step instructions, see the Canvas guide:

https://guides.instructure.com/m/4152/l/1658577-how-do-i-submit-an-assignment-on-behalf-of-a-student-as-an-instructor