If the exchange settles a contract on its own, there are no charges for the client outside of STT.
The STT (Securities Transaction Tax) charge is therefore the only charge he has to pay on his own. If there are any “In the Money” Options in the client’s account on Expiry Day, there is a difference. After the market closes, both the NSE (National Stock Exchange) and BSE (Bombay Stock Exchange) themselves square-off these positions at a higher STT of 0.125% (STT of delivery) instead of the normal STT charge of 0.05%.
For example, if a client has a 8700 Nifty Call option at Expiry and the market closes above 8700, the Client will be charged 8700 * 25 * 0.125% = Rs 271.88 per contract held. This is quite a hefty price to pay. Therefore, it is highly recommended to avoid paying unnecessary charges. Square off your Options contracts before expiry day!