Comment on STT Trap - Options Expiry - NSE BSE MCX-SX
The criteria is if you leave any in the money option position open on market closing, you’ll be charged STT @ 0.125% on the contract value (Strike+Premium)*Lot Size.
So make sure you close all ITM options.
Here’s the NSE Link: http://www.nseindia.com/products/content/derivatives/equities/sec_tranc_tax.htm
Look for “Sale of an option in securities, where option is exercised”