In IIT BHU, the least required attendance is 85 percent for each course. The majority of the students find the attendance rule a little bit annoying but do not oppose it. This is because if students fail to maintain the required minimum attendance, the institute takes disciplinary measures. They may not get permitted to appear in the end semester exam or their registration for the course may get canceled. Students who fail to keep 85% attendance are often awarded Z grade for the course. This grade appears in the grade card until they complete the course with success. No one wants to do something which reflects badly on their future. Moreover, almost every IIT has such rules.
There is no special remedy for casual absenteeism. Only in special cases, the students are granted leave. If a student has health issues, then they can remain absent. They will have to submit an application for his absence with a proper medical certificate. Also, if a student has to go to other places for any competition, then they can ask for leave. The college grants leave if a student really needs it.