Within QuickBooks it is possible to invoice against existing sales orders and create a link between the sales order and the invoice, similarly it is possible to achieve that when importing invoices into QuickBooks using Zed Axis.
To link an invoice to a sales order in the invoice mapping select the field called Link To Sales Order and map that to the column in your import file which contains the Reference number of the Sales Order you wish to link to. When the invoice is imported a link will be created between the two transactions.
Points to consider:
- The customer on the sales order should match the customer on the invoice otherwise QuickBooks will return and error
- The items on the sales order should match those on the invoices.
- When importing the invoice you do not need to import the items again as they will be automatically entered from the linked sales order.