when we return good to the seller then it is sales return so he issues credit note and when some returns good which we sold so how can we issue credit note ?

A credit note serves as an evidence that credit has been granted to a debtor.

When we return certain goods to a seller, in that case, the seller will issue a Credit Note (being his Sales Return).

When certain goods are returned to us, in that case, we being the seller issue a Credit Note (being our Sales Return).