Regarding Missing bill in R1

asheeq ua (ca ipcc) (313 Points)

09 November 2020  
Hi everyone..One of my client had sold pickup on Sep 2020 which was used for business purposes..
But we did not declare that amount in SepGstr 1. However we had disclosed in 3b of sep.

1. Now my question is should I amend R1 of Sep ?
Or can I disclose in October Gstr1 ?

2. If I do R1 of October, How to disclose Hsn Summery in R1 ? (i.e. HSN Code, Descripttion, UQC)

Awaiting for your reply,
Asheeq Abubaker