SCN raised by officer for mistake in Gstr1

Dear Friends,

Non-Taxable Sales were wrongly shown as Taxable in Gstr-1 return for the FY 2018-19.
However, it was shown properly as Non-Taxable in Gst-3B return and this Tax was not paid.
The mistake made by us in Gstr-1 return was then rectified in the Annual Gst-9/9C return.

A Show Cause notice has now been raised by the GST officer where he is asking us to pay the tax amount based on the Gstr1 ret

Is there any notification saying that the Gst-9/9C is the final to be considered for the purpose of scrutiny?