Debit Note

Yes. Debit note can be issued in case there is a variation in price subsequent to sale and issuance of invoice.

To issue credit note or debit note its responsibility of supplier(seller)

As per sec 34 sub sec (1),(3)

Debit note : when tax charged in invoice is less than actual tax

Credit note : when invoice tax is higher than actual tax

In simple words credit note can be issue to decrease the tax amount and debit note issue to increase the tax amount

Tax difference may be result of defeciency of quantity or excess quantity charged in invoice compare to actual quantity