Hello,

You need to take your caste certificate while filling application form for JEE MAINS because JEE MAINS cut off is published considering the caste criteria and you will get the desired college if your marks in JEE MAINS lies according to the cut off criteria of your caste only.

You need to upload it in the registration form otherwise your marks will be considered under general category only since its a national level exam. Also you should show it at the time of admission also to avail admission under your category. So both the processes are important.

All the best!