If I purchase 50 shares of Glenmark @ 800 other 50 shares @ 790 then brokerage will be charged at (20+20) or only 20 rupees, a single script is traded but different orders are placed?

Note that Equity delivery brokerage is Rs 0 with Zerodha. So you don't pay anything.

For intraday, the brokerage is charged for every 'successfully executed order'.

In the example you gave above, if both the transactions are part of 1 order then you pay only Rs 20. It doesn't matter how many transactions order is completed in exchange.

If they are part of different orders placed, then separate brokerage of Rs 20 for each order is charged.

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