Students who are born on or after October 1, 1992 are eligible to apply. Candidates belonging to Scheduled Caste (SC), Scheduled Tribe (ST) and Persons with Disabilities (PwD) have been given a relaxation of 5 years.
Aspiring candidates should have appeared for the Class XII (or equivalent) examination for the first time in either 2016 or 2017.
The candidates must have secured at least 75% marks or be in the top 20 percentile in the 12th Class Examination conducted by respective boards.
For SC/ST students, there shall be a relaxation of 5% in this criterion. Aadhar card is mandatory for all the Indian citizens who are taking JEE.

So you must have passed your +2 for admission in iit