Non-Institutional Investor (NII) is SEBI's formal name for the investor category colloquially called HNI. The defining criterion is bid size above ₹2 lakh — there is no maximum cap. NII applicants cannot bid at cut-off and must specify a price within the band.
SEBI further sub-divides NII into two buckets effective 2022: Small NII for bids between ₹2 lakh and ₹10 lakh, and Big NII for bids above ₹10 lakh. Each sub-bucket has a separate reservation within the overall 15% NII allocation — typically split as Small NII 33% and Big NII 67% of the NII portion.
The sub-bucket split was introduced after SEBI observed that very large NII bids — often leveraged via IPO funding — were dominating allotment on hot issues and crowding out smaller HNIs. Splitting the bucket gives smaller HNIs a better proportional chance.