There needs to be a direct relationship between the GDN and the sales invoice in order to display the GDN number on both the GDN and the sales invoice. This is particularly relevant for part deliveries as it will allow the customer to easily match the correct delivery note with the correct invoice. In a situation where multiple deliveries of the same product and quantity are made against the same sales order in a short space of time, and the customer requests proof of delivery, how can we provide a signed delivery note that is clearly related to the invoice for which the POD is being requested without a linking GDN number on both documents?