gst return query

Ambris Pande (Student) (165 Points)

17 November 2017  
If mistakenly a supplier has missed an invoice and added missing amount in outward sales in gstr-3b and paid the taxes and filled the return.
Now when gstr-1 is filled also missed the invoice nd receiver updated the gstr-2 nd gstr-3 is calculated acc to gstr-1 nd gstr-2 do they need to pay extra tax or not ?
if yes do they have to pay the late fee too or not ?
Please suggest