Dear Abhishek, if you have chosen your category as OBC while filling up the application form and in sub category you chose BC-D, when the merit list is prepared and your name is shortlisted, it is shortlisted based on this Category. And so when you are attending the counselling and admission, it is important to submit this certificate too. OBC NCL has 27% reservation in NEET. BC-D also comes under this sub category.