SALES INVOICE mistake

You can amend the invoice in Sep GSTR 1 filing. Under amend invoice

Yes amend the invoice in next return

Whether revised invoice can be given?

Mistake was made while filing or in original invoice it self?

Additional question: Since invoice is lesser amount, can he issue debit note instead of amending the invoice?

Yes he can. Provided that the seller is charged less in original invoice it self. For ex:- I am the seller and had issued original invoice physical copy of 10k and same was updated in portal, I later realised that I charged less so I can issue a debit note. If it's merely an typing error in GST portal then amending invoice would be sufficient

Manoj H, thank you for the reply.