=Duplicate Invoices.= There are many reasons, in various lines, why duplicate invoices are desirable and even necessary. Some customers request invoices rendered in duplicate with one copy complete, the other minus the prices and extensions. To accomplish this, it is either necessary to place a piece of paper between the carbon and duplicate invoice in such a manner that the prices and extensions will not copy, or to use a short invoice cut off at the left of the price column, or to use a short piece of carbon paper between the original and second, or duplicate, invoice. It is desirable to make extra copies of invoices or duplicates for the use of various departments of a business, for instance, analysis of sales by salesmen. Where a company employs a large number of salesmen, it is very convenient to file in binders a duplicate copy of all invoices sold by each salesman, using a binder for each salesman. This is preferable to having separate columns in the sales book (sales sheets in binders). The latter method permits each salesman to see what every other salesman is doing. [Illustration: Fig. 13. Sales Sheet for Condensed Billing ] =Department Records.= A separate binder allows each man to consult his record without inconvenience to any other one. In large companies having a traffic department, it is necessary to provide a duplicate copy of each invoice for the record, showing complete details of every charge. A distinction should be made between those firms who make their invoices before the goods are shipped, and those who make the invoices after the goods have been shipped. In the cloak business, for instance, the goods are generally billed before the goods are shipped, the invoice being placed in an envelope and packed with the goods. Ofttimes the goods are manufactured in proper quantities, properly checked from the order to the packers' table, and then packed improperly—some customer receiving too many garments, another, too few. Yet the order will be properly checked. To obviate this difficulty, a scheme was devised whereby the packer received a duplicate typewritten copy of the bill (or invoice) showing everything but the quantities. This makes it necessary for the packer to count all the garments and mark down in pencil on this copy of the bill the quantity of each style and kind to be shipped. Before the goods are shipped, the packer's copy of the invoice, with his quantities marked in lead pencil, is compared with the quantities charged on the sales sheet. This scheme forces the packer to count all garments instead of double checking someone else's figures in an absent-minded, or even neglectful, way.