Expiry date of future stock

I want to know that if I have position in future buy or sale and I forget expiry date.

What is action by stock exchange?

If your futures are cash settled, you will make a profit or loss depending on your future buy/sell price and the price of underlying security.
If it’s settled by delivery of stock ( a recent change in Indian markets), then you will have to take delivery of the stock at your future buy price.

@pbgt29 : please note that not every time a stock future expire on last Thursday of month but can expire mid way too whenever there is a case of corporate action like d-merger /merger /amalgamation etc…example: Arvind ltd future expired yesterday so was CESC few weeks back both due to d-merger.

I think one way you can do is to buy the farthest future, this way you need to rollover only 4 times instead of 12 times per year

E.g. right now i want to buy RELIANCE Future, i will take RELIANCE JAN19 FUT, then in January, i will take RELIANCE APR19 FUT and so on.

But need to check price erosion due to time value, I am not sure if that will impact or not.