Have you noticed reference number in SAP Business One? Such as A/P Invoice, A/R Invoice and Sales Order. Unlike system number, reference number is not mandatory filled but can be helpful, especially when the number of documents is huge.
A reference number can be the number assigned by the customers or vendors. It can record their invoice number or shipping number. This characteristic makes a reference number a safety feature to avoid duplicating a document.
Go to Administration > System Initialization > Document Settings and click Per Document tab, choose the document and from the choices when duplicated customer (vendor) reference No. Occurs.
Users can choose “without warning”, “warning only” or “block release/receipt”. They can also choose whether allow copying customer reference No. to Target Doc.
If you are interested in pick and pack function, please visit Tips of Pick and Pack in SAP Business One.