GST INTEREST URGENT QUERY

Ajnas (Student) (844 Points)

23 March 2021  
February 2021 month GSTR 1 total output Tax Rs. 100000 total input Rs. 60000 out of output tax Rs.100000 it include output tax Rs. 20000 relating to January month 2021 missing invoice included in the February 2021 GSTR 1, February 2021 return is not filed before the due date(ie, 20/3/2021) it is filed on 22 march 2021
My query is about

1.For which amount interest is required to calculate because total output Tax Rs. 100000 it include Rs. 20000 missing invoice relating to January 2021 input tax Rs.60000, for interest calculation current month net liability Rs.60000 we need to calculate interest separately for current month return delay filing and previous month invoice? What is the rate of interest?
Ie, interest 18% on output tax Rs.20000 (previous month missing invoice ) and interest 18% on Rs.60000(Rs.80000-Rs.20000) seperately calculated my calculation is correct?
2.GST interest for delay filinf is calculated on net GST liability, if entire ouput tax is paid through input, for delay filing no interest is chargable am i right?