Debit note is also known as Purchase return and Credit note is also known as Sales return. There is some difference between them as follows :
>>Debit note is used by the business to return the good that he purchased from the supplier. Credit note is used by the customer to return goods purchased by him to the business.
>> The amount of debit sales will be deducted from the gross purchase while the amount of credit sales will be deducted from the gross sales.