GST return related

No if ITC left in ledger after payment of tax then no such payment shall made against ITC balance

No need to pay tax if liability after using credit Ledger is nil.

You can utilize your full ITC balance ( as available in your e-credit ledger ) to dispose off your Output Tax Liability ( other than Interest and Penalty ). There will be no requirement of payment of liability in CASH.

However kindly note that as per Notification No. 94/2020 - Central Tax, dated 22nd December 2020, Rule 86B has been introduced which has imposed 99% restriction of ITC available in Electronic Credit Ledger of Registered Person. This means that 1% of output tax liability needs to be paid in "CASH" w.e.f 01/01/2021 if your aggregate turnover exceeds Rs. 50 lakhs in that particular month.

If all output liability is settoff from ITC then I have to fill any Return under QRMP scheme..

No, you have to file Quarterly 3B & 1

As per GST Notification No. 94/2020 - Central Tax, dated 22nd December 2020, Rule 86B, 1% of output tax liability needs to be paid in "CASH" w.e.f 01/01/2021 if your aggregate turnover exceeds Rs. 50 lakhs in that particular month. If your turnover is less than 50 lakhs then you can set off your entire liability through input tax credit (ITC), no need to pay any cash