In options can i buy any number of lots(quantitiy) or do i have any limit as an individual trader in terms of lots or total amount

General
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You can read all about position limits here - http://www.nseindia.com/products/content/derivatives/equities/position_limits.htm

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Yes you can buy many number of lots and accumulate. (For retail trader)

In single order you can buy only upto the limit of quantity freeze.

http://www.nseindia.com/content/fo/qtyfreeze.xls

But if you place orders one by one and accumulate the options you can do so until the exchange stipulated limit, which is very very high (for a retail trader)

Exchange specified limit

5% of the open interest in F&O (options and futures combined actually) in the same underlying stock/index (in terms of number of shares/units)

Say for example the total open interest of TCS October 14 expiry is 46,75,625.

You can buy and hold around 2,33,000 option shares of TCS.

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Lets Say on may 24th, the bank nifty options of 23000 strike was trading at 50 paise, can i buy 20 lakh shares, i dont know what the total OI on banknifty, is, and does each strike price have a different limit on how much we can buy