Interest u/s 50

guna (Student CMA) (74 Points)

19 November 2020  
Dear sir, I have paid 15L CGST+SGST on 10.02.2018 by direct challan.

but GSTR1 and 3B filed on 20.10.2020..

Then Dept seeking interest from 2018...
whether the dept contention is right?