Suppose you have purchased an item at a rate of Rs.100 however by mistake your supplier has billed you at a rate of Rs.95, and then your supplier may issue a debit note for balance of Rs. 5. In such a case, Supplier issues a DEBIT NOTE or DEBIT MEMO and as a client you have to debit respective purchase amount as quoted in the debit note and credit the supplier account.
Thus Debit Note is a document issued to a party or client stating that the client is supposed to credit the account due to the reasons stated in the document. The various reasons could be purchase return, wrong goods sent or wrong quality of product, rate difference, discounts, commissions, interest, service tax etc.