ITM options positions will attract a physical delivery margin - 50% of the contract value.
Stock F&O are physically settled. Hence, for Long ITM Options, the exchange will block physical delivery margin from expiry minus 4 days. Explained in detail here.
Recently there was a minor tweak in this policy for futures and short options positions. But higher margins are still required for long options positions. The increase in margin starts 4 days before expiry as NSE (NCL/CMPT/43262) mandates it -
|Day (BOD-Beginning of the day)||Margins applicable|
|E-4 Day (Friday BOD)||10% of VaR + ELM +Adhoc margins|
|E-3 Day (Monday BOD)||25% of VaR + ELM +Adhoc margins|
|E-2 Day (Tuesday BOD)||45% of VaR + ELM +Adhoc margins|
|E-1 Day (Wednesday BOD)||70% VaR + ELM +Adhoc margins|