Tax on short term gain on shares

Short term capital gain on sale of equity shares is taxable at the flate rate of 15%. However, if your other taxable income excluding short term capital gain is below basic exemption limit then short term capital gain on sale of shares to the extent of unutilized basic exemption limit will be taxable at slab rate and the rest capital gain will be taxable @ 15%. 

If your sale is through recognised stock exchange then you need to pay @ 15% as specified by CA Mansi Parekh sir, otherwise you need to pay as per slab rates.