1. First create a credit note
2. Go to Sales Invoice / Purchase Invoice
3. Click to Edit the invoice you want to apply the credit note
4. Go to the Transaction tab on the left
5. Click the button Use a credit note
6. Choose the Credit Note you have created from the list, and click Use to apply
2. Go to Sales Invoice / Purchase Invoice
3. Click to Edit the invoice you want to apply the credit note
4. Go to the Transaction tab on the left
5. Click the button Use a credit note
6. Choose the Credit Note you have created from the list, and click Use to apply
