Charges of future trading

Hi ! In future trading are the charges levied only when I transact ot it on daily basis

Nope, Rs 20 when you buy and Rs 20 when you sell. No charges in between. BTW, if you had actually put some effort to search you would have found this amazing invention called the Zerodha Brokerage Calculator.

Ya I know that. But is there any exchange charges or stt etc based on daily closing prices. I heard that there is m2m settlement on daily basis

Nope, charges are applicable only when you trade and not on M2M.

All charges are calculated only on the trade transaction value. Daily settlement prices are only used to calculate your daily profit/loss(daily m2m).