Concept:A credit note is a document issued by a seller to reduce the amount owed by a buyer when the original invoice was overstated.
Explanation:When an importer is overcharged, the exporter must correct the invoice error.
The exporter sends a credit note to show that the importer's account has been credited with the excess amount charged.
This note reduces the amount the importer needs to pay.
A debit note is used for the opposite situation, when the buyer owes more.
A proforma invoice is a quotation, and a letter of credit is a bank payment guarantee.
Therefore, only a credit note fits the case of an overcharge.
Answer:D. credit note