My SIS is Infinite Campus and we can enter an M for a missing assignment through IC.
This does two things:
1) Assigns a zero for points to the assignment, and
2) the assignment is flagged as Missing. Right now I see no way of doing this in Canvas. It will only accept numeric scores.
The M means a lot more than 0. The 0 to me means the student has evidence of work, but it so completely wrong they get 0 points. Or because they cheated/plagiarized.
The M means the student gets no points because their is no evidence. They turned in nothing. This helps to communicate with the parents and students of the reason of the zero. It is particularly important for schools running the Assessment for Learning style.