Missed bill intrest

Interest shall be calculated @ 18% from the due date of that month's Return till the date of filing that return where such invoice is reported.

Ex: Suppose Invoice date is July,2020, the GST shall be paid by 20th August, If not interest shall be levied from 21st August till the date of payment of tax- set off of liability in the return)

Yes, we have to pay interest amount irrespective of the balance in Electronic Ledger