Credit memos are issued by the organization that sent the original invoice to reduce amounts owed when items are damaged or incorrect quantities are received. Debit memos are issued by the organization receiving an invoice to request a reduction in amounts owed when they were undercharged or overcharged. Both debit memos and credit memos reduce outstanding vendor balances in accounts payable systems, but debit memos are issued by the company to the vendor while credit memos are issued by the vendor to the company. Reasons for debit memos include material rejections or reductions in purchase costs, while credit memos may be issued for increased charges or late payment fees.