Many traders trade in options and when the option premium value becomes too less they let it expire . If you have been doing this stop letting your options expire because now you will have to pay more.
You have to pay brokerage on expired options
Before brokerage can be charged on the trades executed on exchanges only. But now brokers can charge brokerage on Expiry / Exercise / Assignment of contracts on EXPIRY. Check the below circular of National stock exchange.
You have to pay more STT
When you buy/sell options stock transaction tax(STT) is levied on the option premium at the rate of 0.017%. But when you let it expire the STT is applied on strike price at the rate of 0.125%. Lets understand it with an example