Building reports like Tax P&L, holdings, turnover reports etc. have been one of the most complex projects at Zerodha. This involves calculations on a first-in, first-out (FIFO) basis since day 1 for stocks bought, transferred in and adjusting for various corporate actions.

What is a simple number on the UI involves calculations on the fly & innovations in how we store and crunch hundreds of billions of rows of data. This post from our tech team talks about some of this.

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