Tax exemption for trading as business

My question is from the point of view of intraday trading. When showing trading as a business, is there an upper limit on 'business expenses' that can be claimed towards tax exemption purposes? For example, the Zerodha Varsity page (http://ift.tt/2hSrkll) shows that expenses towards books, phone/internet bills, rental income etc. count as 'cost'. These could add up substantially - for ex. high speed internet alone could easily add up to 25k per annum. Can all this be used for tax exemption, with no upper limit? Do we have to attach/produce receipts?

How much of income expenses have people on TJ been claiming?

On a side note, would the costs towards algo trading APIs, historical data charges, etc. count as expenses and count towards exemption?

Thanks in advance.

Tax exemption for trading as business