A major cause of duplicate payments is multiple copies of the same supplier invoice being entered in the computer system, but with slight variations on the invoice number that keep the computer from flagging them as duplicate invoices. This is an especially common problem when suppliers issue invoices with leading zeros, since one data entry clerk may enter the zeros, while another may ignore them. It also common for employee expense reports and a variety of utility billings, since these documents have no invoice number. It also happens when an original invoice is not paid on time, so the supplier floods the company with extra copies of the invoice, hoping that one of the copies will eventually be paid.
There is no perfect solution to this problem, but the basic approach is to adopt a standard invoice numbering convention for the data entry staff to follow, thereby introducing some consistency into this aspect of invoice data entry. It can include some of the following rules:
Drop leading zeros. It is also possible to reverse this rule and always use leading zeros, but the extra characters may overflow the computer field for invoice numbers.
Use the packing slip number. If the invoice contains no invoice number and it is related to a physical delivery, then there should be a packing slip that accompanied the delivery. If so, enter the packing slip number as the invoice number. If a duplicate invoice arrives, it must still be matched ...