FY 2019 -20 late filing of GSTR 3B after time limit.

Dear Sir
The last date for availing ITC for the year 2019-20 was 20.10.2020.But I filed the return in form GSTR 3B for March 2020 only on 30/10/2020. I also claim the entire input for the same period.But the GST Department disallowed the input credit and the demand for remitting the input with interest and penalty.Have any exemption for the time limit for the period.Pls give an advice or any revised or new notification against this demand note
Muraleedharan Nair
Kottayam
9447191386