Any trading in stocks without actual delivery of stocks during the day is referred to as intra-day and the gains or the losses accruing from it are treated as 'income from speculative businesses' after paying for the expenses in relation to the same that includes STT or securities transaction tax.
At the same time depending on your gross turnover and net profit or loss amount accruing from intraday trading, there is a requirement of maintaining separate books of account with proper documentation that gives a proof of your expenses made in lieu of the trading and any earnings or loss from them.
Tax @ applicable slab rate is payable for intra-day gains or losses
So, as per rules if you are a resident Indian trading in intra-day markets, tax equivalent to the tax slab rate in which you fall applies on such speculative income. Further you need to shell out amount towards the same in advance in 4 installments as prescribed by the specified dates.
In case you are a non-resident Indian as per tax laws laid down in the Indian Tax laws, TDS on such a speculation income is charged for the fiscal year in which these intra-day trading transactions are undertaken.
If loss is incurred on such intra-day trades in a fiscal year then this can be carried forward and is allowed to be set off against income from speculative transactions only in the immediate four fiscal years.