Extra credit refers to points that are not required. They benefit the students who complete them but do not hurt the students who do not complete them. There are a number of ways of adding extra credit to student grades in Canvas.

Option 1. Extra credit on existing assignments.
This is a very easy way to grant extra credit. If an assignment is worth 10 points and you want to give an extra credit point, you can simply enter 11 points for the students who earned the extra credit.

Option 2. Create an extra credit assignments.
Create an assignment worth 0 points.
Enter the students earned extra credit as the score. As the denominator is 0, any points will be extra.

Option 3: Extra credit weighted category.
If you are using weighted categories, you can add an extra credit category and set it to be worth x% of the course grade. This will display your course as out of (100% + x%) 10x%. Then add extra credit assignments, worth points and enter the students earned points. If a student does not earn points for an assignment, be sure to enter that as 0.
    Caveat – set the extra credit category to be worth 0% until there are graded assignments in all of the other categories. If you do not have graded assignments in the other categories then this category will act like part of the regular grade and will negatively affect the grades of students who have not completed it.