Order No vs PO Number in Express Invoice Posted October 8, 2013 Hi, I think you misunderstood the usage of 'Order number' here. 'Order numbers' are unique identifier to 'Orders', same as 'Invoice numbers' are unique to 'Invoices'. New Orders can be created from 'Orders list'; similar to new invoices can be created from 'Invoices List'. Those are two different things. However, you can convert an existing order to invoice, in which case, original order number is displayed in 'Order' column in 'Invoices list'. So, this is the way to go, if you really want an order number to be displayed in the column and print-outs. From 'Orders list', you can select an order and click 'Invoice' button to generate an invoice from the order. Note that order number generation can be controlled through 'Options->Quote->Order Options...', and it is always unique to each order. I suggest playing with 'converting orders to invoices' to explore different scenarios. Hope this helps!