Profits realized within a period of less than one year will attract short term capital gains tax @ 15% which will be deducted at source by your bank. Tax is calculated and deducted for each transaction. In other words, the profits made in one transaction cannot be set off against the loss made in another. You can, however, file your tax returns
at the end of the year and claim refunds if any.

Profits realized from shares that were held for more than
one year are long term capital gains. From the financial
year 2003 -04 onwards, tax on long term capital gains from
capital markets has been abolished. There is, however,
a transaction tax of 0.15% on all trades. Currently, all dividends are also tax- free in the hands of the investors.