When can I begin checking an assignment?

If you intend to begin grading submissions before the assignment Cut-off date, or if you have not set a Cut-off date, you should check option Require students click submit button in section Submission settings of the assignment settings. 

Note: If Require students click submit button was checked and you later uncheck it, students who did not click on Submit assignment will have to save their submission again. Alternatively, you can submit for them by selecting Submit for grading from their Edit drop-down menu in the View/grade all submissions page.