Hello Aman,

Your Certificate should be issued by the competent authority, If you are allotted the seat, The allotted candidates will have to download their allotment letter and pay the seat acceptance fee. The Document verification will be done at their respective reporting centres. 

You can refer the below given article for the further information.

https://engineering.careers360.com/articles/jee-advanced-counselling-and-seat-allotment

Good Luck!