Dear Applicant,

I hope you are doing well, about your question,

You see if you couldn't answer your b.com exam I.e. all the papers or may be a particular paper, on your marksheet it will be marked as absent. So it will be considered as a backlog. You can go and answer those papers in the next time the college conducts it overall it wont affect you much. So contact your college or the Faculty to give you the desired dates for your exam.

Hope this helps !!