Accounting for cashback received from paytm, freecharge etc.

This is an old question!! however a good one. If you have credits accumulated the treatment will be different. But if its just a cash back due to their offers, treat it as discount received. 

Coming to think about it, even if it is credit accumulated or cash back, both must be shown as discount received. If there is a tax consequence on discount received then create a wallet ledger and report accordingly.