Hi there.

If you are having your 12th board exams this year i.e., you are already done with them or are currently taking your exams or will be taking them in this month itself (which means you are going to be 2018 passed out student, EVEN IF YOU ARE A 2017 PASSED OUT STUDENT); you are definitely eligible for the IISER examination this year in July irrespective of the mains and advance qualification. However, you should score at least 55% (be sure to refer to the current cut-off percentage)in the results of your board exams for further proceedings if you qualify the IISER.

All the best!