When a buyer is undercharged, the seller forwards a **debit note**. A debit note is a document used by a seller to inform the buyer of the amount owed as a result of an undercharge or any other type of error that resulted in the seller not receiving the full amount owed. The debit note serves as a request for payment of the additional amount owed. The seller issues the debit note to correct the mistake in the initial invoice and ensure that they receive the correct payment for the goods or services provided.